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  • 2000-2004
  • 1990-1994  (1,524)
  • 1993  (1,524)
  • General Chemistry  (1,210)
  • Rat  (185)
  • Magnetic resonance imaging
  • Nuclear reactions
  • Physics
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  • 2000-2004
  • 1990-1994  (1,524)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 32 (1993), S. 71-73 
    ISSN: 1436-6215
    Keywords: Rat ; glutamate-induced obesity ; postprandial thermogenesis ; Ratte ; Glutamat-induzierte Adipositas ; postprandiale Thermogenese
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Bei 4 Monate alten Ratten mit Glutamat-induzierter Adipositas wurde die postprandiale Thermogenese über 8 h nach Fütterung von 300, 450 und 600 kJ/kg0,75 einer Pellet-Diät mittels indirekter Kalorimetrie in computergesteuerten Stoffwechselkäfigen mit offenem Kreislauf bestimmt. Bei den adipösen Tieren war die postprandiale Thermogenese nach Aufnahme von 600 kJ/kg0,75 (oberhalb des Energieerhaltungsbedarfs) signifikant auf 40% der Thermogenese der Kontrolltiere reduziert (12,0 gegenüber 31,5 kJ/kg0,75×8 h). Es wird geschlußfolgert, daß die Ratte mit Glutamat-induzierter Adipositas als ein Tiermodell mit beeinträchtigter fakultativer Thermogenese anzusehen ist, die hauptsächlich durch eine Verminderung der sympathischen adrenergen Aktivität verursacht ist.
    Notes: Summary Postprandial thermogenesis was estimated in 4-month-old male rats with glutamate induced obesity after being fed with 300, 450 and 600 kJ/kg0.75 of a pellet diet, respectively by indirect calorimetry in computer-controlled open circuit metabolic cages over 8 h. After an intake of 600 kJ/kg0.75 (above the maintenance energy requirement) postprandial thermogenesis was significantly reduced in the obese animals to about 40% of control rats (12.0 versus 31.5 kJ/kg0.75×8 h). It is concluded that the glutamate obese rat can be accepted as an animal model with impaired facultative thermogenesis, mainly caused by a reduction of sympathetic adrenergic activity.
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  • 2
    ISSN: 1438-2199
    Keywords: Amino acids ; N-Methyl-D-aspartate (NMDA) ; Glycine ; HA-966 ; Rat ; Strychnine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study has been carried out to determine if glycine, an allosteric modulator of NMDA receptor, is involved in the vascular effect induced by the activation of the CNS NMDA receptors.Icv NMDA (from 0.01 to 1µg/rat in the 3rd ventricle) determined a significant increase in arterial blood pressure in conscious freely moving rats. Moreover, the hypertension was associated with behavioural modifications (jumping, rearing, teething and running). Glycine pretreatment (1 and 10µg/raticv), significantly increased the NMDA hypertension. Alone glycine did not cause any arterial blood pressure modification while it induced a slight sedation. HA-966 (an antagonist of the glycine site on NMDA receptor) administration (1–10µg/raticv 5 min before glycine) significantly antagonized the glycine effects on NMDA hypertension. Alone HA-966 neither modified arterial blood pressure nor antagonized NMDA hypertension. In conclusion, our investigations confirm NMDA receptor involvement in cardiovascular function and they demonstrate that in vivo glycine positively modulates NMDA receptor.
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  • 3
    ISSN: 1438-2199
    Keywords: Amino acids ; N-Methyl-D-aspartate (NMDA) ; Glycine ; HA-966 ; Rat ; Strychnine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study has been carried out to determine if glycine, an allosteric modulator of NMDA receptor, is involved in the vascular effect induced by the activation of the CNS NMDA receptors.Icv NMDA (from 0.01 to 1µg/rat in the 3rd ventricle) caused a significant increase in arterial blood pressure in conscious freely moving rats. Moreover, the hypertension was associated with behavioural modifications (jumping, rearing, teething and running). Glycine pretreatment (1 and 10µg/raticv), significantly increased the NMDA hypertension. Glycine alone did not cause any arterial blood pressure modification while it induced a slight sedation. HA-966 (an antagonist of the glycine site on NMDA receptor) administration (1–10µg/raticv 5 min before glycine) significantly antagonized the glycine effects on NMDA hypertension. Alone HA-966 neither modified arterial blood pressure nor antagonized NMDA hypertension. In conclusion, our investigations confirm NMDA receptor involvement in cardiovascular function and they demonstrate thatin vivo glycine positively modulates NMDA receptors.
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  • 4
    ISSN: 1438-2199
    Keywords: Amino acids ; Asphyxia ; Hypothermia ; Glutamate receptors ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Perinatal asphyxia was induced by keeping pups-containing uterus horns, removed by hysterectomy, in a 37°C or a 30°C water bath. Asphyxia for a period of 21–22 min at 37°C led to a 97% mortality within the first 20 min period following delivery. When the asphyctic period was extended to more than 22 min all the pups died following delivery. When the asphyxia was induced at 30°C, 100% of the delivered pups survived and were accepted by surrogate mothers. The protective effect of hypothermia could be observed even when the pups-containing uterus horns were exposed to a 45–46 min asphyctic period. Pretreatment with dizocilpine (0.2 mg/kg s.c.), or 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX) (3–30 mg/kg s.c.), administered to the mothers one hour before hysterectomy, reduced slightly the mortality induced by a 21–22 min asphyctic period at 37°C. An increase in survival following a 22–23 min asphyctic period could only be observed after the highest dose of NBQX.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1459
    Keywords: Dementia ; Human immunodeficiency virus ; Electrophysiology ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Thirty-three HIV-positive patients with clinical signs of dementia according to the 1991 AAN criteria underwent psychometric, electrophysiological and radiological examination and were compared with a group of normal healthy subjects and a cohort of clinically asymptomatic HIV-1-positive individuals of comparable education and social environment. Compared with the other groups, test performance was severely impaired in the demented patients. Results of motor testing and MRI revealed that subcortical structures were not exclusively affected, but most severely and early, thus characterizing the clinical feature in HIV-1-associated dementia. In demented patients a rapid deterioration was observed, leading to death within about 12 months on average, which is a markedly shorter survival time than described in the literature for non-demented HIV-1-positive individuals.
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  • 6
    ISSN: 1432-1459
    Keywords: Wallenberg's lateral medullary syndrome ; Pain sensation ; Temperature sensation ; Magnetic resonance imaging ; Electrophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Thirteen patients with Wallenberg's lateral medullary syndrome (WLMS) were studied. Clinical and magnetic resonance imaging (MRI) evidence demonstrated infarction in the dorsolateral medulla which produced loss of pain and temperature sensation on one side of the face ipsilateral to the lesion in seven patients. However, in another six patients, the infarction in a similar location produced the same sensory loss on the contralateral face. This is the first report of an analysis comparing these two conditions in WLMS patients, confirmed by MRI. The finding of normal blink reflex and somatosensory evoked potentials (stimulation on median nerve) in the two groups of patients may indicate that the impulses travel along the central pathways of touch, vibration and joint position sensation instead of the pathways for pain and temperature, because the patients had normal sensation of touch, vibration and joint position but impairment of pain and temperature sensation. In addition, it is suggested that the pathways of late blink reflex (R2) pass through the medial lemniscus in the ventromedial medulla instead of the spinal trigeminal tract in the dorsolateral medulla. Further, the observation of the much longer lantencies (about 29 ms) of the normal R2 raises the possibility that the impulses may travel along the longer pathways through the opposite medial lemniscus and up to the thalamus or cortex where they project to bilateral motoneurons of the orbicularis oculi muscles. Although the alternative of R2 travelling only by the shorter pathways through the brain stem is not excluded, this is not supported by current data.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 240 (1993), S. 8-12 
    ISSN: 1432-1459
    Keywords: Myotonic dystrophy ; Magnetic resonance imaging ; Mental retardation ; Dementia ; Muscle imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Myotonic dystrophy (MD) is characterized by myotonia, weakness and extramuscular symptoms, including intellectual impairment. We performed magnetic resonance imaging (MRI) of brain and muscle in 25 MD patients: 81% had cerebral atrophy (severe in 36%); 68% had focal white matter lesions, which were large and multiple in 27%. Brain MRI findings correlated with mental impairment; the severity of both correlated with disease duration. Changes in brain and muscle MRI were progressive with time, but independent of each other. Muscle MRI findings were fatty degeneration and loss of bulk. In the calves, the medial gastrocnemius muscles were involved earliest and the posteriortibial muscles relatively spared. In the thighs the vastus muscles were damaged most often and the rectus femoris least. Focal muscle damage was efficiently visualized, sometimes preceding clinical detection. Muscle MRI was less sensitive than conventional methods for early diagnosis, but ideal for follow-up, owing to its non-invasiveness and examiner-independence.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 240 (1993), S. 17-20 
    ISSN: 1432-1459
    Keywords: Cerebellar encephalitis ; Epstein-Barr virus ; Varicella-zoster ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We examined 11 adult patients with cerebellar encephalitis (CE) during the acute phase of the disease and at least 12 months later. Five patients were aged between 23 and 31 years, 3 patients between 43 and 44 years and 3 patients between 60 and 64 years. Serological tests gave evidence of Epstein-Barr virus infection in 4 of the 5 young patients. Two patients had serological evidence of varicella-zoster virus reactivation, whereas the serological findings were negative in all other cases. All patients in the younger and middle age groups recovered within 3–30 weeks after onset of CE. If at all, they had only minor cerebellar deficits at the follow-up examination. Magnetic resonance imaging (MRI) examination performed at the follow-up examination was normal in all of them. In contrast, 2 of 3 patients older than 60 years had persistent cerebellar ataxia following CE. In these patients, MRI revealed infratentorial atrophy. Our data show that the clinical spectrum of CE in adults is wider than assumed so far. In addition to typical cases of CE in young male patients with good recovery, CE may also occur in older patients and give rise to persistent cerebellar ataxia.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1459
    Keywords: Multiple sclerosis ; Spinal cord ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In patients with clinically isolated spinal disease, magnetic resonance imaging (MRI) provides a non-invasive method of detecting surgically treatable causes and is also useful in detecting asymptomatic brain lesions where the cord syndrome is due to multiple sclerosis (MS). We report the findings of spinal and brain MRI in 28 patients with spinal cord disorder due to MS. It was possible to detect intrinsic plaques reliably in the majority of patients (60.7%) with clinical findings of spinal cord MS. The results of MRI are compared with the clinical status and with cerebrospinal fluid findings and evoked potentials.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 240 (1993), S. 113-116 
    ISSN: 1432-1459
    Keywords: Delayed neurological deterioration ; Carbon monoxide ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present two patients with delayed neurological deterioration following apparent recovery from carbon monoxide poisoning in whom magnetic resonance imaging showed abnormalities. In the first patient, cortical grey matter abnormalities were seen without white matter changes. Visual evoked potentials were, however, abnormal. In the second, diffuse white matter lesions were detected. In neither patient were basal ganglia lesions seen.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 240 (1993), S. 251-253 
    ISSN: 1432-1459
    Keywords: Leber's optic neuropathy ; Magnetic resonance imaging ; Parinaud's syndrome ; Oculopalatal myoclonus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Six months after the onset of visual loss a 23-year-old male patient with Leber's optic neuropathy associated with a mitochondrial DNA mutation developed brain stem involvement with Parinaud's syndrome and oculopalatal myoclonus. Magnetic resonance imaging (MRI) revealed a high signal area in the brain stem, corresponding to a hypodense area in the CT scan that did not show contrast enhancement. Distinct diminution but not complete remission of the MRI findings was found in the 5-year follow-up, which was not accompanied by clinical improvement. Although the MRI findings were compatible with a demyelinating lesion, neither extensive evoked potential studies nor spinal fluid examination supported this.
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  • 12
    ISSN: 1432-1459
    Keywords: Hypomelanosis of Ito ; Fetal macrocephaly ; Neonatal epileptic encephalopathy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A severe form of hypomelanosis of Ito is reported, which presented as fetal macrocephaly and neonatal epileptic encephalopathy. Lymphocyte karyotypes were normal. MRI showed an absence of delineation between cortical grey matter and white matter. The prominent neuropathological finding was an abnormal cortical morphogenesis, with the co-existence of cells migrating normally and cells exhibitingarrêt en route or even the complete absence of migration. Intense astrocytic reaction with moderate dystrophie features was prescrit. Juxtaposition of two migration behaviours in the neural cells paralleled the cutaneous findings and reinforced the hypothesis of a genetic chimerism.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 240 (1993), S. 407-409 
    ISSN: 1432-1459
    Keywords: Palatal myoclonus ; Inferior olive ; Pseudohypertrophy ; Head injury ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two patients are described, in whom MRI detected unilateral signal abnormalities in the region of the inferior olivary nuclei, suggesting an early stage of olivary hypertrophy. MRI was performed 4 and 7 weeks respectively after traumatic brain-stem injury. Palatal myoclonus was concomitantly observed in one patient, while the other showed no evidence of segmental myoclonus at the time of examination. The authors conclude that MRI is highly sensitive in the detection of olivary hypertrophy and of traumatic lesions of the dentatorubro-olivary pathway.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 240 (1993), S. 423-426 
    ISSN: 1432-1459
    Keywords: Creutzfeldt-Jacob disease ; Magnetic resonance imaging ; Computed tomography ; Electroencephalography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We describe the MRI changes preceding the onset of myoclonus in two patients whose post-mortem examination confirmed the diagnosis of Creutzfeldt-Jakob disease (CJD). MRI showed changes in the striatum early in the course of CJD (2–6 months after the onset of apathy, interpreted as depression, and 1–2 months before the onset of further clinical symptoms). Only in one patient did electroencephalography record the typical triphasic sharp-waves, 1 month after MRI.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 72 (1993), S. 65-73 
    ISSN: 1432-1440
    Keywords: Nicotine ; Analgesia ; Nociception ; Thalamus ; Spinal cord ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To assess the possible role of nicotinergic control in nociception and pain, experiments were carried out on rats under urethane anesthesia in which nociceptive activity was elicited by electrical stimulation of afferent C fibers in the sural nerve and recorded from single neurones in the thalamus and from ascending axons in the spinal cord. Intravenous administration of nicotine (0.01–0.5 mg/kg) depressed the nociceptive activity evoked in the thalamus and the spinal cord in a dose-dependent way. The maximum depression in thalamus and spinal cord was 40% of control activity and obtained at a dose of 0.025 mg/kg. Likewise, local administration of nicotine to the spinal cord by intrathecal injection (5, 10, and 30 μg) reduced the nociceptive activity evoked in neurones of the thalamus and in ascending axons of the spinal cord, the maximum of the depression being 40% of control activity. The depressant effect of nicotine (0.05 mg/kg) was reduced by mecamylamine (1 mg/kg) but not by atropine (0.5 mg/kg). It is concluded that the antinociceptive effect of nicotine is due to a specific action of the alcaloid at the spinal level.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Archives of gynecology and obstetrics 252 (1993), S. 191-195 
    ISSN: 1432-0711
    Keywords: Anastomosis ; Microsurgery ; Sutures ; Rat ; Uterine horn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study compares two simplified techniques, which use only 2 and 4 sutures respectively, with a conventional technique with 8 sutures for fallopian tube anastomosis. Experimentally these techniques were performed on the uterine horns of fifteen female rats. A 100% patency rate was obtained with all three techniques. No difference in the mucosal, muscular and serosal regeneration was observed in the three groups at 10, 20 and 60 days. Two months after surgery, the serosa, muscularis and mucosal layers were completely continuous in all groups. The operating with 2 sutures (5′ 30″±1′ 10″) was significantly less than with 4 (9′09″±0′55″,P〈0.05 ANOVA) and 8 sutures (15′12″ ± 1′41″,P〈0.05 ANOVA). A minimum inflammatory reaction to sutures was observed in all three groups at 60 days after surgery. The results suggest that with 2 sutures are all that is needed for tissue repair.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 52 (1993), S. 361-364 
    ISSN: 1432-0827
    Keywords: Calcitonin ; Sustained release ; Copolymer depot ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Studies were carried out to determine whether monolithic depot formulations, prepared using lactide:glycolide copolymers, could be used to administer salmon calcitonin (sCT) to rats in vivo. Formulations containing 2, 5, or 10% (w/w) sCT were administered subcutaneously to female Wistar strain rats. Release of sCT was determined by measurement of peptide in plasma using a specific radioimmunoassay and by measurement of residual sCT in the depots after recovery at postmortem. Plasma calcium concentrations and cumulative weight gain of the animals were used to measure pharmacological effects of the released sCT. Release of sCT from the depots was controlled by the copolymer and was sustained for periods up to 10 days. However, the release of sCT from the depots did not significantly alter plasma calcium concentrations, and effects on cumulative weight gain were small and transient. Peptide loading of the formulations was shown to modify sCT release. Maximal release of sCT from depots containing 10% peptide occurred over a 7 to 14-day period postadministration, with 5% sCT release occurred between days 11 and 14, and with 2% sCT, the period of maximal release was between days 11 and 18. Release of peptide from the depots was essentially complete by 21 days postadministration irrespective of the peptide loading. These data suggest that lactide:glycolide copolymer depots may have application for the convenient clinical administration of sCT in metabolic bone diseases.
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  • 18
    ISSN: 1432-0827
    Keywords: Bone ; Nandrolone decanoate ; Ovariectomy ; Bone mechanics ; IGF-I ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Nandrolone decanoate (ND) is an anabolic steroid with a positive effect on bone mass in osteoporotic patients. The mechanism of action, (i.e., reduction of bone resorption and/or Stimulation of bone formation), the ultimate effect on mechanical properties, and the most effective dosage are not yet clear. To address these issues, dose-related effects of the long-term effect of ND on Serum and bone biochemistry, bone mineral content, and bone mechanical properties in ovariectomized (OVX) rats (12 weeks old at the Start of the experiment) were Studied for 6 months. The results were compared with those obtained in agematched, intact, and OVX rats. OVX caused in the femur a significant increase in net periosteal bone formation and net endosteal bone resorption of bone collagen content and torsional strength, and of Serum alkaline phosphatase, osteocalcin, and insulin-like growth factor-I (IGF-I) levels, whereas cortical bone density and calcium/creatinine and phosphorus/creatinine in 24-hour urine were Significantly reduced. Treatment of OVX rats with 1 mg ND/14 days resulted in a Significant increase in periosteal bone formation, femur length, cortical and trabecular bone mineral content and density, torsion stiffness and Strength, and bone IGF-I content, and a decrease in Serum osteocalcin, urinary calcium/creatinine levels, and bone collagen content compared with OVX controls. The higher ND dosage of 2.5 mg/14 days did not improve the results. ND treatment did not reverse all changes induced by OVX to the level of the intact controls. These results indicate that ND acts as an antiresorptive drug and as a bone formation Stimulating drug. Furthermore, the increased bone mass and bone mineral density is associated with improved bone Strength and stiffness and the presence of an increased amount of IGF-I. IGF-I is a growth factor considered to play a role in the maintenance of normal skeletal balance by a paracrine or autocrine mechanism.
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  • 19
    ISSN: 1432-0827
    Keywords: Hyperthyroidism ; Osteopenia ; Bisphosphonate ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Hyperthyroidism, either endogenous or iatrogenic, leads to increased bone turnover and osteopenia. This study was conducted to examine (1) whether thyroid hormone excess in rats causes bone changes similar to those seen in patients with hyperthyroidism, and (2) the effects of the aminobisphosphonate alendronate on the thyroid hormone-induced bone changes. Sprague-Dawley male rats, divided into four groups, received L-thyroxine (T4) 250 μg/kg/day (+T4) or vehicle (-T4) subcutaneously six times per week and alendronate 1.75 mg/kg (+ALN) or vehicle (-ALN) orally twice a week. Rats were sacrificed after 3 weeks of treatment, blood samples were analyzed for serum T4, triiodo-L-thyronine (T3), and osteocalcin, and the proximal tibiae were processed for histomorphometric analysis. Serum T4 and T3 levels measured 20–24 hours after the last injection were 2 to 2.5-fold higher in +T4 groups than in-T4 groups. Serum osteocalcin was significantly (P 〈 0.05) higher in +T4/-ALN group than in the other groups, which were not statistically different from each other. T4 treatment (+T4/-ALN) significantly decreased the amount of cancellous bone volume (-45%) and increased osteoid surface (+254%), osteoblast surface (+111%), and osteoclast surface (+176%) relative to control values. Alendronate increased the bone volume above control values in both T4-treated (+ T4/ +ALN) and untreated (-T4/ +ALN) rats, and prevented the T4-induced increase in bone turnover in +T4/+ALN rats. It is concluded that (1) excess thyroid hormone induces cancellous bone loss associated with high bone turnover in the rat, and (2) this bone loss can be prevented by alendronate through the inhibition of osteoclastic activity.
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  • 20
    ISSN: 1432-0851
    Keywords: Bispecific monoclonal antibody ; Lymphokine-activated killer cell ; Rat ; CD8
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In vivo targeting of lymphokine-activated killer (LAK) cells to tumour deposits by bispecific monoclonal antibodies (bimAb) may be a way to improve adoptive immunotherapy. We developed a bimAb against adherent LAK (ALAK) cells and colon tumour CC531 in Wag rats. The bimAb was produced by somatic hybridization of two mouse hybridomas, one producing monoclonal antibodies (mAb) against CD8 (IgG2b, OX8), and the other producing mAb against a CC531-associated antigen (IgG1, CC52). A bimAb-producing clone was selected by an enzyme-linked immunosorbent assay with CC531 tumour cells. BimAb were purified from ascitic fluid by protein A affinity chromatography. Each of five pooled peak fractions was analysed by flow cytometry for the presence of bimAb. Most bimAb were found in a fraction that was eluted at pH 4.5 from protein A. FPLC analysis of this fraction revealed that no parental antibodies were present. The OX8 × CC52 bimAb greatly increased conjugate formation in vitro between ALAK cells and CC531. Results of51Cr-release assays with CC531 as target cells and ALAK cells as effector cells were not significantly different in the presence or in the absence of the bimAb. The methods we used here, a cell enzyme-linked immunosorbent assay and flow cytometry, are simple methods for development and purification of a bimAb when a functional selection method is not a priori available. The OX8 × CC52 bimAb we developed this way may increase in vivo tumour targeting of ALAK cells and thus augment antitumour effect in vivo.
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  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Child's nervous system 9 (1993), S. 172-175 
    ISSN: 1433-0350
    Keywords: Endocranial calcifications ; Infantile celiac disease-epilepsy ; Computed tomography ; Magnetic resonance imaging ; Electroencephalography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The authors report on five patients (three female, two male) with multiple brain calcifications, infantile celiac disease, and epilepsy. The clinical, neuroradiological, neurophysiological, EEG and evolutional aspects are assessed. The authors propose that all patients with brain calcifications which cannot be traced to other known pathologies should undergo diagnostic tests for a malabsorption syndrome; analogously, patients affected with infantile celiac disease should undergo EEG, followed by a neuroradiological examination if the EEG pattern is found to be altered.
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  • 22
    ISSN: 1433-0350
    Keywords: Magnetic resonance imaging ; Surgical decompression ; Visual recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A 3-year-old boy presented with a 3-day history of total blindness. There were no features of raised intracranial pressure or endocrine disturbance. Magnetic resonance imaging of the brain showed a giant craniopharyngioma measuring 5x3 cm. It was located in the suprasellar region and produced a mass effect with compression of the III and both lateral ventricles. The tumour extended downwards into the pituitary fossa. Urgent surgical decompression and subtotal excision of the tumour resulted in complete visual recovery in the right eye. The left eye remained blind. The blindness might have been caused by direct pressure on the optic nerves and chiasma by the tumour. The lack of visual recovery in the left eye may be the consequence of additional ischaemic insult to the left optic nerve. It is concluded that surgical decompression should be carried out in a patient with a giant craniopharyngioma presenting with total blindness before the condition is considered hopeless.
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  • 23
    Electronic Resource
    Electronic Resource
    Springer
    Child's nervous system 9 (1993), S. 391-393 
    ISSN: 1433-0350
    Keywords: Lissencephalies ; Imaging ; Ultrasonography ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Based on the published literature and on our own experiences in the imaging of lissencephalies with ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI) we propose a strategy for the use of the different methods depending on the clinical symptoms and the age of the patient. In newborns and babies with suspected lissencephaly ultrasound should be used as the first method. If there is a cortical malformation and a more thorough examination seems necessary, CT can be used in type I lissencephaly. However, due to its excellent grey-white matter contrast MRI is the best method for imaging of lissencephalies. Especially in the diagnosis of type II lissencephaly, MRI is definitely superior to CT and US, and so it should be used in all patients with Walker-Warburg syndrome and other congenital muscular dystrophies as well as in all doubtful cases. It must always be remembered that the extent of the cortical dysplasias is quite variable, as is the presence of further malformations.
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  • 24
    ISSN: 1433-0350
    Keywords: Neurofibromatosis type 1 ; Magnetic resonance imaging ; Computed tomography ; Central nervous system imaging abnormalities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report the results of the reevaluation of 24 patients with neurofibromatosis type 1 (NF1) using central nervous system (CNS) imaging techniques. The first examination by computed tomography (CT) or magnetic resonance imaging (MRI) indicated the presence of optic glioma in three cases, “unidentified bright objects” (UBOs) in six, and a suspected right frontal tumor in one. In two patients optic glioma and UBOs were both present and in one of them a bulbar tumor was also suspected. Later imaging examinations revealed the appearance of optic glioma in three more cases and UBOs in nine. In two of these patients both optic glioma and UBOs were present. This study indicates that the likelihood of detecting imaging abnormalities in patients with NF1 increases when systematic follow-up is performed. Optic gliomas are characteristic of pediatric patients; they rarely give rise to clinical manifestations (1/6 cases) and in general progress very slowly. For these reasons, therapeutic strategy must be carefully considered and individually decided. UBOs are very frequent findings in pediatric patients with NF 1 and therefore they must be considered diagnostically relevant. They are not related to clinical manifestations and spontaneous regression has been observed. The nature of these imaging abnormalities is still unknown, but because they do not behave like tumors, useless and dangerous therapeutic procedures should not be employed.
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  • 25
    ISSN: 1433-0350
    Keywords: Glioblastoma multiforme ; CSF dissemination ; Glial fibrillary acidic protein ; Multiple cranial nerve palsy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A 9-year, 6-month-old boy presented with peripheral-type multiple cranial nerve palsy due to extensive cerebrospinal fluid (CSF) dissemination of intracranial glioblastoma multiforme. Tissue obtained from biopsydid not stain for glial fibrillary acidic protein (GFAP). The relationship between GFAP-negative tumor cells and extensive CSF dissemination agreed with recent reports. Magnetic resonance imaging with gadolinium-DPTA enhancement clearly depicted not only the cranial meningeal dissemination but also spinal metastasis. Magnetic resonance imaging showed undoubted usefulness in demonstrating disseminated glioblastoma.
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  • 26
    ISSN: 1433-2981
    Keywords: Anabolic agents ; Haemolysis ; l-Carnitine ; Osmotic fragility ; Rat ; Stanozolol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect on erythrocyte osmotic fragility of two anabolic agents, widely used to improve physical performance, has been studied. These agents, the steroid derivative, stanozolol, and a quaternary amine,l-carnitine, were administered to rats at rest and while performing running exercises, for 12 weeks. The results show that exercise does not alter the haemolysis curve. Administration of both agents in resting condition does increase the osmotic resistance of the erythrocytes. The combined effect of drug administration and physical exercise further increases the osmotic resistance in the case of stanozolol, presumably due to the steroid-erythrocyte membrane interaction as well as by an erthyropoietic effect.
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  • 27
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    Comparative clinical pathology 3 (1993), S. 214-219 
    ISSN: 1433-2981
    Keywords: Creatine kinase ; Lactate dehydrogenase ; Plasma ; Platelet ; Preanalytical conditions ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Marked interlaboratory variation exists in the analysis of various clinical chemistry parameters, particularly in lactate dehydrogenase (LDH) and creatine kinase (CK) activity in the rat. Much of this variation is due to the handling of the animal prior to sampling, the method and site of sampling, and the handling of the sample prior to analysis. Such preanalytical conditions can lead to spurious high values, which in turn may lead to misinterpretation of test article effects in toxicological studies. This paper reviews the literature with respect to preanalytical conditions and their effect on LDH and CK, and reports on our own investigations, in the hope of increasing the awareness among investigators of these problems, leading to the elimination of inappropriate sampling and handling techniques. Our own investigations show that in order to limit variation, the use of serum (as opposed to plasma), bleeding from the retro-orbital sinus and storage by freezing should all be avoided.
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  • 28
    ISSN: 1437-1596
    Keywords: Paraquat ; Immunohistochemistry ; Rat ; Stomach ; Esophagus ; Paraquat ; Immunhistochemie ; Ratte ; Magen ; Osophagus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Die Verteilung von Paraquat im Gewebe des Magens und des Ösophagus von Ratten wurde mittels immunhistochemischer Verfahren bestimmt. Nach intravenöser Applikation von Paraquat wurden Ratten nach Zeitspannen von 3 h, 12 h, 24 h, 3 Tagen und 10 Tagen getötet. Im Magen wurde Paraquat in den Epithelzellen in einem Zeitraum von 24h bis 10 Tagen nach Applikation gemessen, wohingegen im Ösophagus sowohl in den Epithelzellen als auch in der Lamina propria mucosa Paraquat 12 h bis 10 Tage nach Injektion gemessen werden konnte. Obwohl diese Ergebnisse mit Paraquat-Befunden im Intestinum von Ratten korrelieren, konnte keine eindeutige Zeitabhängigkeit der Verteilung beobachtet werden. Dieses Ergebnis führt zu der Annahme, daß Magen und Ösophagus als wichtige Speichergewebe an einer Redistribution von Paraquat beteiligt sind.
    Notes: Summary The dynamics of paraquat in the stomach and esophagus of rats were demonstrated using immunohistochemical techniques. The Rats were killed 3 h, 12 h, 24 h, 3 days, 7 days and 10 days after intravenous administration of paraquat. In the stomach, paraquat was localized in the epithelial cells between 24h and 10 days after injection, whereas in the esophagus, paraquat was localized in epithelial cells and the lamina propria mucosa between 12 h and 10 days after administration. Although these findings were similar to those observed in the intestine of rats, no clear changes in the distribution of paraquat with time were observed; suggesting that the stomach and esophagus are important reservoirs for the redistribution of paraquat.
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  • 29
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    Pediatric surgery international 8 (1993), S. 41-44 
    ISSN: 1437-9813
    Keywords: Testicular ischaemia ; Tubular atrophy ; Paternity ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of testicular ischaemia on fertility as assessed by paternity rate was studied in seven groups of male Sprague-Dawley pubertal rats. Transient unilateral occlusion of the testicular artery and venous outflow was performed for 30, 60, 90, and 120 min using non-crushing microvascular clamps in groups 1–4 (n = 6). Group 5 (n = 12, Fowler-Stephens) had division of both the testicular artery and vein, whereas group 6 (n = 12, Refluo) had division of the testicular artery only. Group 7 (n = 6) consisted of controls upon whom a sham operation was performed. Testicular biopsy 6 weeks after transient testicular ischaemia of 30, 60, and 90 min showed tubular atrophy in 20%–33% of the testes. Ischaemia of 120 min led to tubular atrophy in 84% of testes. Division of only the testicular artery caused tubular atrophy in 58% of testes. Division of both testicular artery and venous outflow was associated with total tubular destruction and necrosis in 78% of testes and 22% had variable tubular atrophy. A paternity rate of 50%–80% was noted in groups 1–4 following transient unilateral testicular ischaemia and contralateral vasectomy. This compared well with the expected 75% paternity rate for a control rat population. Chronic ischaemia (group 5) together with testicular venous interruption was associated with observably lower fertility and a paternity rate of 18%. However, when venous outflow was preserved (group 6), chronic ischaemia after testicular artery division did not affect the paternity rate (50%) significantly.
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  • 30
    ISSN: 1432-2161
    Keywords: Elderly ; Periscapular mass ; Magnetic resonance imaging ; Short T2 ; Elastofibroma dorsi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Elastofibroma dorsi is a rarely made radiological diagnosis. The rarity of the condition, lack of a suitable imaging modality, and an inconsistent clinical approach in evaluating indeterminate soft tissue tumors has contributed to this failure. With magnetic resonance imaging now being recognized as the examination of choice for all indeterminate soft tissue tumors, a prebiopsy diagnosis can frequently be made by radiologists familiar with the characteristic periscapular location, predilection for elderly females, and short T2 on magnetic resonance imaging.
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  • 31
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    Skeletal radiology 22 (1993), S. 187-190 
    ISSN: 1432-2161
    Keywords: Occipital condyles ; Fracture ; Computed tomography ; Pathogenic mechanism ; Neurologic damage ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fractures of the occipital condyle are rare; 32 cases have been reported in the literature.Here, the authors describe four additional cases of occipital condylar fracture. Anderson's classification is used: type I fracture: comminution of the condyle without significant displacement; type II: basilar fracture extending into the condyle; type III: condylar avulsion. The possible mechanisms are identified. Computed tomography proved essential in diagnosing these fractures; coronal reconstructions together with axial scans are particularly helpful. Three-dimensional reconstruction did not prove essential in diagnosing these fractures.
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  • 32
    ISSN: 1432-2307
    Keywords: Ultrastructure ; Morphometry ; Diabetic nephropathy ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Morphological and morphometric studies of glomeruli were carried out in streptozotocin-induced diabetic rats using improved tissue processing and computerized morphometry. Increased mesangial matrix, occupying the enlarged diabetic mesangium, contained an abundance of dark granular material in addition to the microfibrils which were usually found in the control glomeruli. In the diabetic glomeruli, the lamina densa was thick and heterogeneous showing a dense layer both on its epithelial and endothelial aspects, and the lamina rara externa contained more fibrils than in control rats. Detailed estimation of the absolute values of the various compartments of the diabetic glomeruli by using perfusion-flxed materials and a computer-assisted digitizer revealed that the volume and surface area of the mesangium were increased more extensively than those of the capillary; the enlargement of the mesangial-capillary interface area was the most pronounced among the morphometric changes of the diabetic glomeruli; and that the moderate increase in capillary volume was associated with an increased radius. Our quantitative results showed that capillaries in the diabetic glomeruli had an extensively wider neck which may be the first sign of structural damage to the glomerular tuft.
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  • 33
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    Mycopathologia 123 (1993), S. 149-154 
    ISSN: 1573-0832
    Keywords: Ascending pyelonephritis ; Candida albicans ; Experimental model ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We developed a new experimental model of ascendingCandida pyelonephritis in female rats with leukopenia and vesicoureteral reflux. Rats were treated transperitoneally with cyclophosphamide (200 mg/kg) to induce leukopenia 3 days before and transurethrally with diluted acetic acid solution to induce vesicoureteral reflux 1 day before inoculation ofCandida albicans strain, ATCC 10259 (containing 107 cells). Microscopy revealed acute pyelonephritis in whichCandida cells invaded from the fornix and/or papilla into the medulla within 3 days after inoculation. Between 7 and 28 days after inoculation, chronic pyelonephritis reached the cortex. The incidence of pyelonephritis increased gradually and was approximately 80% after 7 days.Candida colony counts of bladder urine specimens obtained by direct puncture were significantly greater in rats with pyelonephritis extending into the parenchyma than in those with pyelonephritis located along the pelvis (p〈0.01). These results suggest that this rat model shows the characteristic feature of ascending pyelonephritis due toC. albicans and that the severity ofCandida pyelonephritis can be estimated fromCandida counts of bladder urine.
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  • 34
    ISSN: 1432-0533
    Keywords: Focal cerebral ischemia ; Middle cerebral artery occlusion ; Pathology ; Penumbra ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Male Fisher rats (n=61) underwent permanent focal cerebral ischemia induced by left middle cerebral artery (MCA) occlusion, in conjunction with ipsilateral common carotid artery ligation. The experiments were terminated at time points ranging from immediately following occlusion to 30 days post MCA occlusion. A coronal histological section, in close proximity to the site of the arterial occlusion, was taken from each brain and divided into six areas encompassing the affected cortex and caudate putamen. Each area was analyzed for ischemic damage according to a grading scale that reflects changes in neuronal morphology. Differential neuronal counts were also made on a 0.5-mm2 field in each of the six areas. The areas closest to the occluded vessel showed accelerated ischemic damage between 8 and 12 h after occlusion, leaving open the possibility that before 8 h, therapeutic intervention may be effective. After 12 h, changes in these areas progressed to complete necrosis and eventual cavitation with a complete loss of neurons after 10 days. The areas more peripheral to the occluded vessel exhibited mild ischemic damage, with an apparent reversal of damage grading at later time points and no loss of neurons. This reversal of ischemic damage in the peripheral areas is suggestive of a histological equivalent of the penumbra.
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  • 35
    ISSN: 1432-0568
    Keywords: Immunohistochemistry ; Neuropeptides ; Rat ; Substance P ; Superior cervical ganglion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Four types of substance P-immunoreactive structures have been distinguished in the rat superior cervical ganglion by double-immunofluorescence microscopy: (1) A major population of mainly varicose fibres enmeshed singly-scattered neuronal perikarya, some of which contained vasoactive intestinal polypeptide-immunoreactivity. These substance P-immunoreactive fibres did not contain colocalized calcitonin gene-related peptide (CGRP) and were absent after transection of the cervical sympathetic trunk. (2) A rather small substance P-immunoreactive fibre population with colocalized calcitonin gene-related peptide-immunoreactivity was distributed in a patchy manner and disappeared after cutting the postganglionic branches. (3) Most of the intraganglionic small intensely fluorescent (SIF) cell clusters were intensely substance P-immunoreactive. SIF cells were not visibly changed in number and fluorescence intensity by either surgical procedure. (4) Immunoreactivity was not visible in principal ganglionic neurons of control ganglia, but occurred in cell bodies after pre- as well as after postganglionic nerve transection. Some of the substance P-immunolabelled perikarya in addition revealed immunostaining to antisera against the catecholamine-synthesizin enyzme tyrosine hydroxylase or against the neuropeptides leu-enkephalin and vasoactive intestinal polypeptide, respectively. The results strongly suggest that, in addition to a substance P-containing preganglionic input (1), and a supply by substance P-containing sensory axon collaterals (2), the superior cervical ganglion of the rat gives origin to a paraganglionic (3) and a postganglionic (4) substance P-immunoreactive intrinsic system, the latter becoming visible only after disconnection of the sympathetic pathway.
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  • 36
    ISSN: 1432-0568
    Keywords: Cochlea ; Development ; Rat ; Innervation ; Efferent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The baso-apical distributions of the myelinated nerve fibres (representative for the inner hair cell afferent fibres) and the outer hair cell efferent fibres were studied during postnatal development of the rat cochlea. The myelinated fibres were counted in the primary osseos spiral lamina from semi-thin sections. The outer hair cell efferent fibres were counted in the tunnel of Corti by means of ultra-thin sections. The developmental changes of the myelinated fibres were investigated between 8 and 60 days after birth (DAB); those of the outer hair cell efferent fibres between 20 and 30 DAB. Between 12 DAB (onset of hearing) and 20 DAB the baso-apical distribution of the myelinated fibres does not change. Striking maturational changes occur late after the onset of hearing, between 20 and 30 DAB. The innervation density of the myelinated fibres increases in the lower middle region of the cochlea. In this region a maximum of innervation density appears. The efferent fibres to the outer hair cells show at 20 DAB a maximum of innervation density in the middle of the cochlea but between 20 and 30 DAB, the fibre density decreases in this region. During the same period the maximum of innervation density shifts towardsthe base. The change in the innervation densities of the myelinated fibres and the outer hair cell efferent fibres occurs late in development, after the onset of hearing, and after the organ of Corti shows an adult-like appearance.
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  • 37
    ISSN: 0942-0940
    Keywords: Magnetic resonance imaging ; angio MR ; phase contrast magnetic resonance ; spinal cord arteriovenous malformations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In spite of the recent advances in neuroradiology including the CT scan and the spin-echo-magnetic resonance (MR), accurate diagnosis of arteriovenous malformations (AVMs) involving the spinal cord is still based on selective angiography. This last procedure is invasive and needs to be repeated during the follow up. Phase contrast angio MR was performed with a 0.5 Tesla unit on 12 patients with an AVM involving the spinal cord (7 intramedullary AVMs, 4 perimedullary fistulas, and 1 dural fistula with perimedullary venous drainage); 4 of these were investigated before and after treatment. Angio MR showed abnormal vascular patterns within the spinal canal in all cases, without distinguishing between arteries and veins; the nidus of the intramedullary AVMs was displayed in all cases. Angio MR provided images of the whole AVMs comparable to the angiographic pictures, in contrast to the spin-echo MR, which provided only discontinued images of the vessels. The efficient range of velocity providing images varied, according to the type of the malformation (slow for dural fistulas, rapid for intra-medullary AVMs). In the 4 patients investigated after treatment, comparison of the images obtained before and after treatment permitted assessment of the degree of occlusion of the malformation. Finally, angio MR as a complement of spin-echo MR can now be used as a reliable tool for detection of spinal cord AVMs, assessing the indication for angiography, and, furthermore, it can probably replace most of the postoperative control angiographies. The value of the efficient imaging velocity is disputable but seems to depend on the haemodynamic characteristics of the malformation and may then serve as a guide to angiography.
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  • 38
    ISSN: 1432-0533
    Keywords: Ethanol ; Rat ; Optic nerve ; Morphometry ; Axons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of chronic ethanol exposure on number and calibres of optic nerve axons (and number of retinal ganglion cells) were investigated in a rat model. Male Sprague-Dawley rats were fed a liquid, ethanol-containing diet for 5, 10 and 17 weeks with littermates given isocaloric amounts of ethanol-free diet serving as controls. After fixation by perfusion, the optic nerves were imbedded in epoxy resin and sectioned for electron microscopy. Systematic random sampling was made from a cross-shaped area over the nerve. Axons within a counting frame were counted and morphometrically categorized with regard to mean diameter and the total number of axons estimated from number per area and the cross-sectional area of the nerve, which was measured using a digitizer table. According to non-parametric statistical analysis, ethanol exposure resulted in a significant reduction in mean cross-sectional area of the optic nerve and in mean axonal calibre but not in total axonal number in the ethanol-treated rats but there was no significant effect of duration of the exposure. The mean cross-sectional area of the nerve was reduced by 9%, 10% and 18% after 5, 10 and 17 weeks of exposure, respectively. The reduction in cross-sectional area appeared to be related to a proportional reduction in axonal and myelin area fractions. The findings indicate that chronic ethanol exposure results in decreased axonal calibres without axonal loss. This also implies that there is no reduction in the number of retinal ganglion cells.
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  • 39
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    Anatomy and embryology 187 (1993), S. 291-297 
    ISSN: 1432-0568
    Keywords: Tail gut ; Tail cord ; Secondary body formation ; Gut ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The secondary body formation is a developmental mechanism occurring in the caudal part of the embryo in which embryonic structures arise from a mass of mesenchymal cells without previous formation of germ layers. The formation of the tail gut by this mechanism was investigated on transverse serial semithin and ultrathin sections of 12-, 13-, 14- and 15-day rat embryo tails. The tail gut, together with the tail portion of the notochord, originates from an axial mass of condensed mesenchymal cells named tail cord. Formation of the tail gut involves the appearance of large intercellular junctions among tail cord cells, and rearrangement of these cells around a newly formed lumen. Mesenchymal characteristics of these cells are gradually lost, and they simultaneously acquire the morphology of epithelial cells. Some cells of the tail cord, located ventral to the tail gut, do not participate in the tail gut formation and form a separate mass of cells without any definitive morphogenetic fate. This surplus group of cells is first evident in 12-day embryos, and it increases in mass during the following 3 days. In 15-day embryos, after the tail gut has completely disappeared, the surplus cells represent all that remains of the tail cord. The mesenchymal-epithelial transformation of the tail cord cells into the cells of the tail gut, and the appearance of the surplus cells, could be considered as the main morphological arguments for the secondary formation of the tail gut.
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  • 40
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    Dysphagia 8 (1993), S. 235-238 
    ISSN: 1432-0460
    Keywords: Dysphagia ; Brainstem stroke/infarction ; Magnetic resonance imaging ; Swallowing ; Deglutition ; Deglutition disorders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ten patients with clinically probable brain-stem stroke presenting primarily as acute dysphagia but without visible brainstem abnormality by MRI are described. The patients were evaluated with neurologic examinations, cinepharyngoesophagography, and brain MRI studies. Each patient solely or predominately experienced sudden pharyngeal dysphagia, and additional symptoms or signs other than dysphonia or dysarthria were scarce. Small vessel disease or cardiac embolism were the apparent causes of what appear to have been very discrete brainstem strokes in these patients. Acute pharyngeal dysphagia can be the sole or primary manifestation of brainstem stroke. A negative MRI study should not preclude consideration of this diagnosis, if brainstem stroke is otherwise clinically probable.
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  • 41
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    Surgical and radiologic anatomy 15 (1993), S. 21-29 
    ISSN: 1279-8517
    Keywords: Liver anatomy ; Large inferior right hepatic vein ; Magnetic resonance imaging ; Intraoperative ultrasonography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Les vv. hépatiques droites moyennes et inférieures sont très fréquentes voire constantes, mais le plus souvent de petit diamètre. L'existence d'une v. hépatique droite inférieure de grand diamètre, le plus souvent unique, entraine une variation dans le drainage veineux du lobe droit du foie. Les vv. hépatiques droites inférieures atteignant ou dépassant 0,5 cm de diamètre ont été recherchées sur 125 préparations anatomiques du foie : 70 pièces d'injection-corrosion, 32 foies embaumés au formol et sur des coupes du tronc frontales ou frontales-obliques effectuées chez 23 cadavres. La fréquence de ces veines a été estimée à 9 % sur les pièces d'injection-corrosion, 13 % sur les coupes et 16 % sur les foies embaumés au formol. Dans la littérature, la fréquence de ces veines varie de 10 % à 24 % selon la méthode employée pour les reconnaitre. naitre. Un balancement équilibré existe le plus souvent entre les vv. hépatiques droites supérieure et inférieure. Exceptionnellement la v. hépatique droite inférieure est prédominante par rapport à la v. hépatique droite supérieure. La situation d'une v. hépatique droite inférieure de grand diamètre est constante, à proximité de la face viscérale du foie. Le territoire qui lui est propre est le segment VI, mais il peut déborder un peu sur les segments voisins. En clinique, l'existence d'une v. hépatique droite inférieure de grand diamètre, reconnue par l'IRM et surtout repérée par l'échographie per-opératoire, permet de réaliser une hépatectomie sub-totale en ne conservant que le segment VI. Dans certaines circonstances pathologiques, grâce au développement des anastomoses entre les vv. hépatiques, une v. hépatique droite inférieure de grand diamètre peut contribuer à une suppléance circulatoire en direction de l'atrium droit.
    Notes: Summary The right middle and inferior hepatic vv. are very frequent, indeed constant, but usually of small caliber. The presence of an extra-wide right inferior hepatic v., usually solitary, produces a variation in the venous drainage of the right lobe of the liver. The right inferior hepatic vv. reaching or exceeding a caliber of 0.5 cm were investigated in 125 anatomic liver specimens: 70 injection-corrosion specimens, 32 formolised livers and frontal or frontal-oblique sections of the trunk made in 23 cadavers. The incidence of such vv. was estimated at 9% in the injection-corrosion specimens, 13% in the sections and 16% in the formolised livers. The incidence of these vv. in the literature varies from 10% to 24% according to the method used to demonstrate them. Usually, there is a balance between the right superior and inferior hepatic vv. Rarely, the right inferior hepatic v. predominates compared with the right superior hepatic v. The position of an extra-wide right inferior hepatic v. is constant, close to the visceral aspect of the liver. Its appropriate territory is segment VI, but it may encroach somewhat on adjacent segments. Clinically, the existence of an extra-wide right inferior hepatic v. as detected by MRI and, especially, located by intraoperative ultrasonography, allows performance of a subtotal hepatectomy leaving only segment VI. In certain pathologic conditions, thanks to the development of anastomoses between the hepatic vv., an extra-wide right inferior hepatic v. may contribute to a compensatory circulation towards the right atrium.
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  • 42
    ISSN: 1432-1106
    Keywords: Neural transplantation ; Fetal grafts ; Huntington disease ; Neural regeneration ; Neural development ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fetal striatal grafts are found to have a modular organization revealed by acetylcholinesterase (AChE) histochemistry. The AChE-rich zones represent the only portions of these grafts that are anatomically and functionally integrated into the host brain. In this study, the medial and lateral ganglionic eminences (MGEs and LGEs) were selectively dissected from the basal telencephalon of embryonic-day-14 (E14) rat fetuses to compare their relative contributions to the AChE-rich fraction of intrastriatal grafts. Separate cell suspensions prepared from either eminence were stereotaxically implanted into excitotoxically lesioned neostriatum of adult rats. Eight weeks after transplantation, grafts of the MGE were compared with those of the LGE with respect to the proportion of AChE-rich zones, graft size, graft morphology, and afferent dopaminergic innervation as revealed by tyrosine hydroxylase (TH) immunostaining. The mean AChE-rich fraction in LGE grafts (87%±4%) was markedly greater than the AChE-rich fraction in MGE grafts (25%±10%). The LGE grafts were also morphologically better incorporated into the lesioned host striatum, partially reconstituting the striatal morphology. There was no statistically significant difference in graft size between the two groups. The AChE-rich LGE grafts were TH immunoreactive, whereas the AChE-poor MGE grafts were not. We conclude that grafts derived exclusively from the fetal LGE reconstitute the striatal morphology and consist almost entirely of AChE-rich zones.
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  • 43
    ISSN: 1432-1106
    Keywords: Basal ganglia ; Nigrostriatal pathway ; Plasticity ; Dendritic spines ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Destruction of the dopamine-containing neurons in the rat substantia nigra results in morphological changes in the striatum which have been characterized at both the light and electron microscopic levels. After a unilateral 6-hydroxydopamine injection into the medial forebrain bundle, Golgi-impregnated medium-sized spiny neurons in the neostriatum ipsilateral to the injection had a lower density of spines on their dendrites than those on the contralateral side. A similar decrease in spine density was apparent from 12 days until at least 13.5 months after the lesion. A bilateral loss of spines occurred with increasing age regardless of the presence or absence of the nigrostriatal dopaminergic pathway. At the ultrastructural level, the general pattern of synaptic input to the Golgi-impregnated medium-sized spiny neurons was similar on both sides of the brain. The most obvious class of afferent boutons contacting these spiny neurons formed prominent asymmetrical synaptic specializations with the heads of the spines. The numbers of asymmetric synaptic profiles counted in random electron micrographs from the striata ipsilateral and contralateral to the lesion were not significantly different from each other. A small but significant increase in the length of asymmetric synaptic specialization profiles was, however, detected in the striata lacking a dopamine input.
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  • 44
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    Experimental brain research 93 (1993), S. 95-103 
    ISSN: 1432-1106
    Keywords: Glutamate ; Aspartate ; Gamma-aminobutyric acid ; Transmitter colocalization ; Postembedding immunolabeling ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Anterogradely labeled corticospinal axons and their terminals were identified after injections of wheat germ-agglutinin conjugated to horseradish peroxidase in the sensorimotor cortex of rats. Thin myelinated axons were labeled in the corticospinal tract. Terminal labeling was densest in the internal basilar nucleus and laminae III–IV of the dorsal horn throughout the spinal cord; electron microscopical observations were mainly from the cervical enlargement. Labeled terminals were most often small and dome-shaped with densely packed, clear round vesicles and sparse mitochondria. These terminals established asymmetric synapses with small dendrites or spines and were never involved in axoaxonic contacts. Postembedding immunocytochemistry was used to study the subcellular distribution of glutamate, aspartate, and gamma-aminobutyric acid (GABA). Corticospinal terminals appeared enriched in glutamate, but not GABA. Some corticospinal terminals appeared enriched in aspartate, though the labeling was less selective than in the case of glutamate. GABA immunolabeling was very dense in about 20% of terminals. These were most often small, rich in mitochondria, and made symmetric synapses; they were not anterogradely labeled from the cortex. Quantitative analysis on double immunolabeled material allowed a direct comparison of particle density for different antigens in the same section. Terminals with a high density of particles coding for glutamate were not enriched with GABA, and terminals immunolabeled for GABA were not enriched with glutamate. There was no significant correlation between glutamate and aspartate immunolabeling in corticospinal terminals; a subpopulation of these terminals may be enriched in aspartate. Aspartate immunolabeling was consistently higher in dendrites postsynaptic (in the plane of section) to corticospinal terminals than in other dendrites. That neither aspartate nor GABA was enriched in dendrites postsynaptic to GABAergic terminals suggests that the phenomenon is not a generic feature of synapses.
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  • 45
    ISSN: 1432-1106
    Keywords: Acoustic startle response ; Amygdala ; Basal ; nucleus of Meynert ; Pontine reticular formation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The acoustic startle response (ASR) is a simple motor reaction to intense and sudden acoustic stimuli. The neural pathway underlying the ASR in rats is already fairly well understood. As the ASR is subject to a variety of modulations, this reaction can serve as a model for vertebrate neuroethologists to investigate the neural mechanisms mediating sensorimotor transfer and their extrinsic modulation. We report here on experiments in rats which were undertaken in order to investigate the neural mechanisms underlying the enhancement of the ASR. An increased amplitude of the ASR can be observed during states of conditioned and unconditioned fear. By employing neuroanatomical tract tracing methods, we describe a pathway from neurons of the medial division of the central amygdaloid nucleus (cA) and the basal nucleus of Meynert (B) to the caudal pontine reticular nucleus (PnC), an important relay station in the acoustic startle pathway. Extracellular recordings from acoustically responsive neurons in the PnC showed that electrical stimulation of the cA/B facilitates the tone evoked response of these neurons. Behavioural tests following chemical stimulation of the cA/B with NMDA (N-methyl-d-aspartate) in awake rats indicated that activation of this pathway increases the ASR. The lack of sufficient spatial resolution of our stimulation techniques did not allow us to differentiate the relative contributions of the cA and the B to this effect. As the amygdaloid complex has been implicated in emotional behaviour, particularly in the mediation of fear, these findings substantiate the concept that the amygdaloid complex plays a key role for the enhancement of the ASR by conditioned and unconditioned fear.
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  • 46
    ISSN: 1432-1106
    Keywords: Nerve growth factor ; Electrophysiology ; Transplant ; Brain ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have investigated the electrophysiological effects of nerve growth factor (NGF) on single-neuron activity in central nervous system (CNS) grafts of septum, spinal cord, and hippocampus in oculo. NGF was found to have slow-onset, long-lasting excitatory effects on the spontaneous firing of neurons in septal grafts, while no such effects were found in neurons of either hippocampal or spinal cord grafts. Pretreatment with an antibody against the p75 low-affinity NGF receptor blocked the NGF-induced excitations. A second NGF application caused much stronger excitatory responses in sensitive neurons. Our data suggest that forebrain cholinergic neurons may be selectively sensitive to NGF also at the neurophysiological level, responding by excitations, and that NGF upregulates these responses within less than an hour.
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  • 47
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    Experimental brain research 93 (1993), S. 279-287 
    ISSN: 1432-1106
    Keywords: Valproate ; Anticonvulsant ; Sodium inactivation ; Patch clamp ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cultured rat hippocampal neurons with short processes were investigated using the whole cell voltage clamp under conditions appropriate for isolating Na+ currents. After incubation of the neuron culture for a period of 15–30 min in 1 mM sodium valproate, several parameters of the Na+ current were changed. The peak Na+ conductance g p, measured using hyperpolarizing prepulses, was reduced by valproate in a voltage-dependent manner. In the membrane voltage range from -30 to +20 mV, this reduction showed a linear dependence on voltage, increasing from about zero to approximately 30% of g p, the maximum peak Na+ conductance of the neuron. At the holding voltage of -70 mV, the inactivation parameter h t8 decreased from 0.88 in the control to 0.64 in the valproate solution. This reduction originated mainly from a 10 mV shift in the sigmoid relation between h t8 and membrane voltage along the voltage axis to hyperpolarizing potentials. The decay of the maximum peak Na+ current (inactivation) could be fitted by a biexponential function. Time constants of the fast and slow component at -20 mV decreased in valproate by about 50%. Valproate also retarded the recovery from inactivation, as determined at the holding voltage. The sigmoid recovery from inactivation could reasonably be described by an exponential function with time constant τ r and delay time Δt. Both τ r and At increased more than 200% in valproate. Our results indicate that valproate affected the Na+ current in hippocampal neurons in a way that contributed to a considerable depression of Na+ reactivation. This explains the frequency-dependent inhibition of action potentials as observed in mammalian central nervous tissue and may be the principal action of the anticonvulsant.
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  • 48
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    Experimental brain research 93 (1993), S. 293-298 
    ISSN: 1432-1106
    Keywords: Medial vestibular nucleus ; 5-Hydroxytryptamine ; Serotonin ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of 5-hydroxytryptamine (5-HT) and related compounds on the discharge rate of tonically active medial vestibular nucleus (MVN) neurones were studied in an in vitro slice preparation of the dorsal brainstem of the rat. The majority (87 of 107, 82%) of MVN neurones were excited by 5-HT. Nine cells (8%) showed a biphasic response to 5-HT, which consisted of a brief inhibition followed by excitation. Eleven cells (10%) were inhibited by 5-HT. The excitatory effects of 5-HT were mimicked by alpha-methyl-5-HT and antagonised by ketanserin and ritanserin, indicating the involvement of the 5-HT2 subtype of 5-HT receptor. In biphasic cells, blockade of 5-HT2 receptors by ketanserin reduced the excitatory component of the response and revealed an enhanced initial inhibition. The inhibitory effects in biphasic cells, and in cells that showed a pure inhibition in response to 5-HT, were blocked by pindobind-5-HT and mimicked by 8-hydroxy-2-(di-n-propylamino)-tetralin indicating the involvement of 5-HT1A receptors. The significance of these findings in relation to the effects of 5-HT on vestibular reflex function is discussed.
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  • 49
    ISSN: 1432-1106
    Keywords: c-fos ; FOS ; Basal forebrain ; Excitatory ammino acids ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract These experiments investigated, by studying patterns of c-fos expression, the distribution of neurons activated or destroyed by the infusion into the basal forebrain of various excitatory amino acids at toxic and subtoxic doses. The results of experiment 1 showed that N-methyl-d-aspartic acid (NMDA), quisqualic acid and αamino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) differentially increased the expression of c-fos in magnocellular cholinergic nucleus basalis, dorsal and ventral pallidal neurons. AMPA was the most, and NMDA the least, effective in inducing FOS in nucleus basalis magnocellularis (nbM) neurons, with quisqualic acid having an intermediate effect, whereas the reverse was true in terms of the induction of FOS in pallidal neurons. In experiment 2, it was demonstrated that, in animals with ibotenic acid-induced lesions of the basal forebrain that were targetted on the nbM, virtually no pallidal neurons could be visualized that expressed FOS following AMPA-induced excitation of the dorsal and ventral striatum. By contrast, in animals with AMPA-induced lesions of the nbM, excitation of the striatum was followed by the expression of FOS in many dorsal and ventral pallidal neurons. Thus, infusions of AMPA into the basal forebrain appears preferentially to activate or destroy, depending on the concentration infused, cholinergic nbM neurons, whereas ibotenic acid or NMDA preferentially destroys or activates neurons of the dorsal and ventral pallidum. These results provide novel and complementary information regarding the organization of the basal forebrain and allow a clearer understanding of the different behavioural consequences of NMDA agonist-induced and non-NMDA agonist-induced excitotoxic lesions of this area.
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  • 50
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    Experimental brain research 94 (1993), S. 1-15 
    ISSN: 1432-1106
    Keywords: Visual cortex ; Extrastriate visual areas ; Striate-extrastriate connections ; Fluorescent tracers ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous studies have determined that the striate cortex of the rat is reciprocally connected with multiple extrastriate cortical areas that are retinotopically organized. The objective of this study was to investigate the retinotopy of the striate-extrastriate connections in the rat, by placing triple or double injections of fluorescent tracers (fluorogold, fast blue, rhodamine dextran, or rhodamine-labeled microspheres) in different regions of the striate cortex (Oc1) and mapping the distribution of cells and fibers labeled with the different tracers in the lateral (Oc2L) and medial (Oc2M) extrastriate cortex. The tracer injection sites were visualized in tangential sections of the flattened cortex and correlated with the myelin layout of the striate cortex and with an electrophysiological map from previous studies. The results showed retinotopically organized Oc1 connections with ten different extrastriate cortical areas. The location of these extrastriate areas and the retinotopy of their striate connections remained mostly invariant despite changes of the injection sites in Oc1. Thus, the quadrantic retinotopy was obtained for striate connections to areas posterior, posterolateral, lateromedial, laterointermediate, laterolateral, anterolateral and rostrolateral in Oc2L; and to areas posteromedial, anteromedial, and anterior in Oc2M. The present anatomical map correlates well with electrophysiological maps of the rat extrastriate cortex from previous studies. Furthermore, they provide a definition of the retinotopy of some areas that have not been completely mapped before. These results reaffirm the existence of multiple extrastriate visual areas in the rat.
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  • 51
    ISSN: 1432-1106
    Keywords: Cortical malformation ; Status verrucosus ; Focal cortical dysplasia ; Porencephaly ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Different types of cortical malformation were produced, following focal cortical freezing, electrocoagulation, focal cortical aspiration or gentle brushing of uncovered meninges, in newborn or 1-to 3-day-old rats. Malformations included laminar necrosis of the cerebral cortex, status verrucosus, focal cortical dysplasia reminiscent of microgyria, and porencephaly. Similar procedures from postnatal day 4 onwards, at a time when a reactive astrogliosis is possible, produced cavitating infarcts and tissue scars. Cytoarchitectonic studies revealed an abnormal distribution of different types of pyramidal and nonpyramidal neurons in these malformations. These indicated three subtypes of focal cortical dysplasia, which probably depend on different pathogenic mechanisms. Autoradiographic studies with [3H] methylthymidine showed normal positioning of late-generated neuroblasts in the cerebral cortex, thus suggesting preserved migration. The present experimentally induced cortical malformations are useful models of similar cortical abnormalities in humans.
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  • 52
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    Experimental brain research 94 (1993), S. 193-202 
    ISSN: 1432-1106
    Keywords: Ubiquitin ; Heat shock protein 72 kD ; c-Fos ; Entorhinal cortex ; NMDA ; Neuronal loss ; Alzheimer's disease ; Stress protein ; Neurodegeneration ; Neurotoxicity ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The entorhinal cortex (EC) appears to be one of the earliest regions to express cellular pathology in aging and Alzheimer's disease. The relationships between cellular stress protein responses and the temporal and spatial aspects of cell death induced by N-methyl-D-aspartate (NMDA) was investigated in this anatomical region. Low doses of NMDA were infused stereotactically into the medial EC of the rat. At intervals starting from 0.5 h up to 7 days after a 1.25-μl EC infusion of 15 mM NMDA, 30 mM NMDA, or saline, the expression of ubiquitin (Ub), 72-kDa heat shock protein (HSP 72), and c-Fos was determined in relation to neuronal death. Volumes of entorhinal Ub- and HSP 72-like immunoreactivity peaked between 18 and 48 h after either 15 or 30 mM NMDA infusions. After 15 mM NMDA infusions, maximal volumes of HSP 72- and Ub-like immunoreactivity in the EC at 48 h were similar to the subsequent maximal volume of neuronal loss in the EC seen after 96 hours. After infusion of 30 mM NMDA, the final EC volume of neuronal loss seen at 7 days after NMDA corresponded to 70–80% of the maximal HSP-Ub stress protein response seen at 2 days, implying that a population of HSP 72- and Ub-immunopositive cells survived the NMDA insult. C-Fos expression as determined by immunoreactivity for the nuclear phosphoprotein (Fos) indicated neuronal activation at NMDA infusion sites, in the perirhinal cortex, hippocampus, and other sites throughout the injected hemisphere. In the EC, c-Fos immunoreactivity returned to baseline levels by 8 h, well before the dramatic increases in HSP 72 and Ub volumes. Our results demonstrate that HSP 72 and Ub expression in vivo precedes and correlates with, but does not necessarily lead to, neuronal death following glutamate receptor-mediated toxicity in the EC.
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  • 53
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    Experimental brain research 94 (1993), S. 371-392 
    ISSN: 1432-1106
    Keywords: Cortical dynamics ; Optical recording ; Voltage sensitive dyes ; Visual cortex ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We monitored optical signals from cortex stained with a voltage sensitive dye to study activity evoked by intracortical electrical stimulation. The objectives were to study the spatial and temporal spread of activity from intrinsic connections near the stimulating electrode and to develop a new technique to study extrinsic projections from striate cortex to extrastriate target areas. Various measures were made of the time course of the optical signal (latency, rise time, decay time, temporal summation, facilitation versus depression, and presence or absence of a slow undershoot); in general, these measures were found to vary significantly across different response positions, different experiments, and even different runs within the same experiment. The spatial distribution of responses near the stimulating electrode in striate cortex was usually elliptical and was most often elongated along the anterior-posterior axis, with a typical size (full width at 75% max) of 1.3 mm (anterior-posterior axis) by 0.75 mm (medio-lateral axis). In some cases, complex spatio-temporal patterns were observed, in which the position of the maximum optical signal shifted with time or split into multiple peaks. In eight experiments, a response focus was found in extrastriate cortex at an expected location within the lateromedial area (LM). The response focus in LM was typically about half the size of that in striate cortex. In some experiments we observed additional focal responses in the anterolateral visual area (AL). The extrastriate responses showed a significant delay (3–10 ms) in onset and time to peak relative to the striate response. The validity of this technique for determining extrinsic projections was tested in two types of experiments. In the first, stimulation from two electrodes in striate cortex generated response foci consistent with the known topographic organization of area LM. In the second, the optically measured response focus was shown to correlate with the histologically reconstructed projection of a chemical tracer injected near the site of stimulation. We discuss the chain of neurophysiological events that occur during and after focal electrical stimulation and how they relate to the observed optical signal. We conclude that direct passive responses were a small component of our signal, that the component due to action potentials in directly stimulated neurons should have occurred in the first 1–2 ms post stimulus and is small compared to the peak signal, and that overall our signals were probably dominated by a combination of asynchronously occurring action potentials and excitatory and inhibitory synaptic potentials. These results, together with the prospect of being able to trace many connections in a single experiment, indicate that the combination of optical recording and focal electrical stimulation provides a valuable means for analyzing structural and physiological aspects of cortical circuitry.
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  • 54
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    Experimental brain research 95 (1993), S. 65-69 
    ISSN: 1432-1106
    Keywords: Calcium channels ; Glutamate ; Patch clamp ; Cerebellar granule cells ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Voltage-dependent calcium channels of cerebellar granule cells maintained in a Ca2+-free depolarising solution were recorded using the cell-attached configuration of the patch-clamp technique. An increase in the maximum open probability of calcium channels and a shift in their activation curve toward more hyperpolarising potentials were found in the presence of glutamate, a natural, excitatory amino acid. Such an increase in the activity of calcium channels was not due to ionic fluxes activated by glutamate, and was probably produced by a second messenger pathway triggered by the binding of glutamate to its receptor.
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  • 55
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    Experimental brain research 95 (1993), S. 70-76 
    ISSN: 1432-1106
    Keywords: Protein synthesis ; Ischemia ; Hippocampus ; Reactive astrocytosis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two groups of rats were subjected to 12 min of global cerebral ischemia and 6 days recirculation using the four-vessel occlusion model with hypotension and then treated with the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) antagonist NBQX [2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxa-linedione (Honoré et al. 1988). One group was used for routine and quantitative histology and immunostaining for glial fibrillary acidic protein (GFAP). The second group was subjected to autoradiographic studies of regional cerebral protein synthesis, with special emphasis on the hippocampus, the frontal cortex, and the thalamus. It was found that neuroprotective treatment with NBQX normalized cerebral protein synthesis rate (CPSR) in all investigated regions 6 days after ischemia. In untreated ischemic animals CPSR was normalized in all regions except for the CA3 and thalamus, where it had increased by 29% and 41%, respectively. Treatment of controls with NBQX had no effect on CPSR after 6 days. The histological investigations revealed that NBQX did not protect vulnerable cells in the dentate hilus and the reticular thalamic nucleus (RTN). In these regions reactive astrocytosis visualized by GFAP immunostaining was equally pronounced in both ischemic and NBQX-treated animals, and most neurons in the RTN were eosinophilic. The 80–100% pyramidal neuron loss in CA1 was accompanied by a high degree of reactive astrocytosis, whereas the NBQX-treated animals showed no signs of astrocytosis in this region. The ischemic CA1 pyramidal layer was also massively invaded by microglia. Together these observations strongly suggest that the quantitatively normal protein synthesis in this region after ischemia must be attributed to these glial cell populations.
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  • 56
    ISSN: 1432-1106
    Keywords: Fibroblast growth factor receptor ; Basic fibroblast growth factor ; Forebrain ischemia ; Astrocyte ; In situ hybridization ; Hippocampus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recently, we demonstrated that transient forebrain ischemia in rats leads to an early and strong induction of basic fibroblast growth factor (bFGF) synthesis in astrocytes in the injured brain regions. In this study, in order to clarify the targets of such raised endogenous bFGF levels, the messenger RNA (mRNA) expression of its receptors (flg and bek) at in the hippocampus following transient forebrain ischemia induced by four-vessel occlusion for 20 min was investigated using an in situ hybridization technique. Transient forebrain ischemia induced an increase in the number of flg mRNA-positive cells from an early stage (24 h after ischemia) in the hippocampal CA1 subfield where delayed neuronal death occurred later (48–72 h after ischemia). This increase became more marked with the progression of neuronal death and was still evident in the same area 30 days later. The time course of the appearance and distribution pattern of flg mRNA-positive cells in the CA1 subfield were quite similar to those of bFGF mRNA-positive cells. On the other hand, in situ hybridization for bek mRNA showed only slight and transient (observed 72 h and 5 days after ischemia) increases in the number of mRNA-positive cells in the CA1 subfield following ischemia. The use of in situ hybridization and glial fibrillary acidic protein immunohistochemistry in combination demonstrated that the cells in the CA1 subfield that exhibited ischemia-induced flg or bek mRNA expression were astrocytes. These data indicate that transient forebrain ischemia induces upregulation of fibroblast growth factor-receptor expression, accompanied by increased bFGF expression in astrocytes, and suggest that the increased astrocytic bFGF levels in injured brain regions act on the astrocytes via autocrine systems and are involved in the development and maintenance of astrocytosis.
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  • 57
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    Experimental brain research 95 (1993), S. 477-487 
    ISSN: 1432-1106
    Keywords: Electrophysiology ; Medulla oblongata ; Spinal cord ; Interneurons ; Respiratory control ; Intracellular labelling ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Upper cervical inspiratory neurons form a distinct neuronal column located near the lateral edge of the intermediate grey matter in the rostral spinal segments. Previous studies conducted in cats have demonstrated synaptic inputs to these neurons from several respiratory related regions of the medulla, and long descending axonal projections mainly towards the motoneurons supplying the intercostal muscles. The aim of this study was to examine the electrophysiological and morphological properties of this propriospinal system in the rat. Extracellular recordings were made from 127 cervical inspiratory units, mainly in the C1 and C2 segments. Eighty-two percent could be antidromically activated from the C7/C8 border. No evidence of monosynaptic connection was obtained by cross-correlating the activity of some of these units with the discharge of the phrenic nerve. Intracellular recordings were made from seven neurons, three of which were labelled with biotinamide (neurobiotin). Long “survival times” after intracellular injections (up to 23 h) resulted in staining of axons for long distances, at least to the C5 segment. Each of the three labelled axons issued only one short collateral which arborized in the region of the phrenic nucleus. These results demonstrate that upper cervical inspiratory neurons in the rat have features similar to those previously described in the cat, including only a limited projection to the phrenic nucleus. In addition, this study provides the first morphological identification of these neurons.
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  • 58
    ISSN: 1432-1106
    Keywords: Spinal cord ; Arthritis ; Nociception ; Joint ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of this study was to determine the discharge and receptive field properties of spinal cord neurons with ankle input in spinal segments L4-6 in the rat, both under control conditions and during the course of an adjuvant-induced unilateral inflammation in the ankle. The extent of receptive fields in the skin and deep tissue was assessed using brush, pinch and compression stimuli. Neurons were categorized as nociceptive-specific or wide-dynamic-range neurons on the basis of their response thresholds and responses to suprathreshold stimuli. At all stages of inflammation (2, 6, 13 and 20 days post inoculation) the population of neurons with ankle input showed differences from the population of neurons with ankle input in control rats. There was a reduction in the number of neurons that appeared as nociceptive specific and a concomitant increase in the number of neurons showing a wide-dynamic-range response profile. The receptive fields of the neurons with ankle input were markedly larger in rats with inflammation in the ankle region and mainly spread proximally on the ipsilateral hindlimb and also to the abdomen and tail in some cases. There was also an increase in the number of neurons with contralateral excitatory inputs. The mechanical thresholds at the ankle joint and proximal parts of the ipsilateral hindlimb were less in arthritic rats than in controls. The proportion of spontaneously active neurons was also increased in rats during the initial and later stages of inflammation, although there was no significant increase in the mean spontaneous discharge frequency. These data show that there are long-term changes in the receptive field and response properties of neurons in intact rats with chronic unilateral adjuvant-induced inflammation similar to those described previously in spinal cats with acute inflammation (Neugebauer and Schaible 1990). It is presumed that similar afferent and spinal mechanisms are at work under acute and chronic inflammatory conditions which produce hyperexcitability in spinal neurons with joint input.
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  • 59
    ISSN: 1432-1106
    Keywords: Platelet-derived growth factor ; Dopaminergic neurons ; Cell culture ; Parkinson's disease ; Rat ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of two isoforms of platelet-derived growth factor (PDGF), PDGF-AA and PDGF-BB, was tested on dissociated cell cultures of ventral mesencephalon from rat and human embryos. PDGF-BB but not PDGF-AA reduced the progressive loss of tyrosine hydroxylase- (TH)-positive neurons in rat and human cell cultures. The mean number of TH-positive cells in the PDGF-BB-treated rat culture was 64% and 106% higher than in the control cultures after 7 and 10 days in vitro, respectively. Corresponding figures for human TH-positive neurons were 90% and 145%. The influence of PDGF-BB was specific for TH-positive neurons and not a general trophic effect, since no change of either total cell number or metabolic activity was found. In PDGF-BB-treated cultures of human but not rat tissue the TH-positive neurons had longer neurites than observed in control or PDGF-AA-treated cultures. These data indicate that PDGF-BB may act as a trophic factor for mesencephalic dopaminergic neurons and suggest that administration of PDGF-BB could ameliorate degeneration and possibly promote axonal sprouting of these neurons in vivo.
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  • 60
    ISSN: 1432-1106
    Keywords: c-fos ; FOS ; Striatopallidal system ; Subthalamic nucleus ; Nucleus basalis magnocellularis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In these experiments, induction of the immediate early gene c-fos following excitation of striatal neurons has been used to investigate the organization of the ventral and dorsal striatopallidal systems and the relationship between striatal neurons and cholinergic neurons of the nucleus basalis magnocellularis (of Meynert, nbM). The results demonstrate that FOS immunoreactivity (ir) can be detected in ventral and dorsal striatal neurons following infusions of the non-N-methyl-d-aspartic acid (NMDA) glutamate receptor agonist α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA). This activation and increased expression of FOS in striatal neurons was itself associated with the sustained appearance of FOS-ir in neurons of the ipsilateral ventral and dorsal pallidum, subthalamic nucleus and some thalamic nuclei. Infusions of AMPA into the ventral striatum (VS), but not the dorsal striatum (DS), also resulted in the appearance of FOS-ir in a proportion (17%) of the cholinergic neurons of the nbM. By combining the retrograde transport of Fluoro-Gold with FOS immunocytochemistry, it was also possible to demonstrate that approximately 46% and 58% of the pallidal neurons containing FOS-ir after infusions of AMPA into the VS or DS, respectively, directly project to the subthalamic nucleus. Taken together, these observations suggest that visualizing the protein product of transsynaptic c-fos induction provides an effective way to study the topographic and transsynaptic, within-system consequences of striatal activation.
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  • 61
    ISSN: 1432-1106
    Keywords: Calcium entry blockers ; Transient cerebral ischaemia ; Aminergic neurotransmitters ; Microdialysis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cerebral ischaemia induces considerable neurotransmitter exocytosis, mediated by calcium entry in neurones, essentially via the N-type, voltage-dependent channels, which are insensitive to calcium blockers. Nonetheless, these blockers, by unclear mechanisms, exert a neuroprotective effect when used in experimental ischaemic models. On the other hand, the existence of L-type, voltage-dependent channels, the only ones responding to the action of calcium blockers on synapses, argues in favour of their possible concomitant action in certain highly pathological situations. We studied the action of three calcium blockers, nimodipine, diltiazem and verapamil (administered at a concentration of 100 μM directly into the striatum of rats), on the extracellular release of dopamine and serotonin, and on the level of their main metabolites, in a model of transient global cerebral ischaemia (four-vessel occlusion). The total absence of effect of these molecules on neurotransmitter release induced by ischaemia proves the non-involvement of this mechanism in the protective action of calcium entry blockers on ischaemic lesions, and the absence or very weak action of L-type, voltage-dependent presynaptic channels in the striatum of rats.
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  • 62
    ISSN: 1432-1106
    Keywords: Hippocampus ; Caudate ; Extrastriate visual cortex ; Memory ; Dissociation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Based on behavioral procedures aimed at measuring working or data-based memory for spatial location, response, and visual object information, it is shown that there is a triple dissociation among the hippocampus, caudate nucleus, and extrastriate visual cortex in mediating spatial location, response, and visual object information, respectively. The hippocampus appears to subserve only spatial location, the caudate nucleus only response, and the extrastriate visual cortex only visual object information. The results support the neurobiological foundation of the attribute memory model.
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  • 63
    ISSN: 1432-1106
    Keywords: Calcium-binding protein ; Calbindin ; Colloidal gold ; Quantitation ; Intracellular concentration ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The immunointensities of calcium-binding proteins parvalbumin (PV) and calbindin D28K were quantified in different parts of Purkinje cells and interneurons (basket cells and stellate cells) of the rat cerebellum. An electron microscopic, postembedding immunogold procedure on Lowicryl K4M-embedded thin sections was applied. Neuronal profiles were identified by double-labeling immunocytochemistry using the combination of the two primary antibodies, mouse monoclonal anti-rat calbindin D28K and rabbit polyclonal anti-rat PV. The secondary antibodies were conjugated with colloidal gold of different sizes (10 and 15 nm diameter). In the cerebellar cortex, double-labeled profiles were identified as Purkinje cells and profiles labeled only with anti-PV were identified as inteneurons. The densities of gold particles were used for statistical comparison of the relative levels of PV and calbindin D28K in somata, dendrites, dendritic spines, axons and axon terminals of Purkinje cells, and interneurons. The axons and axon terminals of Purkinje cells and basket cells had significantly higher levels of PV immunoreactivity than Purkinje cell somata, primary, secondary, and tertiary dendrites, and dendritic spines, as well as interneuron somata. On the other hand, the present study could not determine conclusively whether calbindin D28K was distributed homogeneously throughout soma, dendrites, and axons of Purkinje cells or was also concentrated in Purkinje cell axons. To estimate absolute PV concentrations, we made a series of artificial standard samples which were aldehyde-fixed 10% bovine serum albumin containing given concentrations of PV (0, 12.5, 25, 50, 100, 200, and 400 μM, 1 and 2 mM), and calibration curves were deduced from quantitative immunogold analyses of these standard samples. We also analyzed a fast twitch muscle, the superficial part of the gastrocnemius muscle (GCM), whose PV content was previously reported in a biochemical study; the comparison between gold particle densities of GCM and standard samples indicated that these artificial standard samples could be used to estimate the approximate intracellular concentrations of PV. Based on these analyses PV concentrations were estimated as 50-100 μM in Purkinje cell somata and dendrites as well as interneuron somata, and as 1 mM or more in axons and axon terminals of Purkinje cells and basket cells.
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  • 64
    ISSN: 1432-1106
    Keywords: Lateral perforant pathway ; GABAB ; Presynaptic inhibition ; Hippocampus ; Facilitation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Paired-pulse potentiation of the glutamate-mediated excitatory postsynaptic potential (EPSP) recorded in the dentate gyrus molecular layer is thought to be mediated presynaptically. It is known that the activation of adenosine (A1) and GABAB receptors results in the reduction of glutamate release in the dentate molecular layer via presynaptic mechanisms. To examine possible modulatory roles of these receptors on paired-pulse potentiation, we examined the effects of adenosine and baclofen (a GABAB agonist) on paired-pulse potentiation using extracellular recording from the lateral perforant path in rat hippocampal slices maintained in vitro. We compared these effects with those of l-α-amino-4-phosphonobutyric acid (l-AP4) over a wide range of interstimulus intervals (ISIs). l-AP4 enhanced paired-pulse potentiation over the full range of ISIs tested (40–800 ms), whereas adenosine enhanced paired-pulse potentiation only at ISIs of 40–100 ms. In contrast, baclofen reduced paired-pulse potentiation only at ISIs of 400–800 ms. Furthermore, baclofen increased the amplitude of lateral perforant path field potentials, previously reported to be baclofen-insensitive. These results suggest that paired-pulse potentiation can be modulated through the activation of adenosine and baclofen receptors, indicate that this modulation is dependent on ISI, and show that there are at least two pharmacologically separable components of paired-pulse potentiation in the dentate gyrus.
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  • 65
    ISSN: 1432-1106
    Keywords: Sympathetic nerve ; Superior cervical ganglion ; Neonatal development ; Cerebral arteries ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to clarify the developmental pattern in the sympathetic nerve fibers innervating the cerebral arterial system during the postnatal period in rats, we labeled the postganglionic nerve fibers originating in the superior cervical ganglion (SCG) and directly observed their extension and plexus formation by means of anterograde labeling with wheat germ agglutinin-horseradish peroxidase (WGA-HRP). The WGA-HRP solution was injected into the right SCG 1–7 days after birth. The rats were killed 48 h after trace injection, and the cerebral arteries were reacted with tetramethylbenzidine, then observed as a whole mount preparation. The labeled nerve fibers appeared as a few relatively straight bundles with branching fibers running longitudinally to the long axis of the artery in the ipsilateral right side of the circle of Willis and proximal portion of their main branching arteries at 3 days after birth. The nerve fibers started to form a circular pattern of nerve plexus only on the wall of the circle of Willis as early as 1 week after birth. At the beginning of postnatal week 2, labeled nerve fibers extended the collateral projections into the collateral side of the circle of Willis, and these expanding projections could not be observed at postnatal week 3. We observed a route of the sympathetic nerve fibers advancing into the cerebral arterial system which has not been described in previous studies; bundle of labeled nerve fibers entered into the wall of the middle portion of the basilar artery in half of the animals, in any postnatal period. We were able to confirm, by using an anterograde labeling technique with WGA-HRP, how the sympathetic nerve fibers advance into the cerebral arterial system, when they start to form nerve plexus during the postnatal period in rats, and clarified that the sympathetic nerve fibers showed overabundant collateral projection in the cerebral arterial system during the early postnatal period.
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  • 66
    ISSN: 1432-1106
    Keywords: Oxytocin ; Opioids ; Vasopressin ; Naloxone ; Cross-tolerance ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spontaneous electrical activity of oxytocin-secreting neurones in the rat supraoptic nucleus is depressed by the mu-opiate receptor agonist morphine, leading to a reduction in plasma oxytocin concentration. In the present experiments, the electrical activity of single neurones was recorded from the supraoptic nucleus of urethane-anaesthetized rats. For 5 days prior to the experiments the rats had received a continuous infusion of either morphine or vehicle into a lateral cerebral ventricle; this regimen of morphine treatment results in tolerance to, and dependence upon, morphine in the central mechanisms controlling oxytocin secretion. Intravenous injection of the specific kappa- opioid agonist U50,488 at low doses resulted in small but significant increases in the electrical discharge activity of some putative oxytocin neurones in both morphine-treated and morphine- naive rats. At higher doses, the kappa-agonist consistently inhibited almost all cells tested. Morphine-treated rats, despite showing tolerance to morphine itself, showed no cross-tolerance to the inhibitory actions of U50,488 upon the oxytocin system. In separate experiments both morphine and U50,488 were effective in inhibiting supraoptic neuronal activation evoked by stimulation of the region anterior and ventral to the third ventricle, and activation following systemic injection of cholecystokinin, suggesting that both opioids act upon the final common pathway — the oxytocin neurone itself.
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  • 67
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    Experimental brain research 94 (1993), S. 301-307 
    ISSN: 1432-1106
    Keywords: Bulbocavernosus reflex ; Spinal nucleus of the bulbocavernosus ; Androgen ; Testosterone ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The bulbocavernosus (BC) reflex, produced in the BC motor nerve in response to electrical stimulation of the contralateral pudendal sensory nerve, was investigated in intact, castrated, and testosterone-treated castrated male rats under urethane anesthesia. No significant group differences in the reflex latency, sensory or motor conduction velocity, or central delay were observed. A conditioning pulse to the pudendal sensory nerve caused suppression of the averaged antidromic field potential recorded in the contralateral spinal nucleus of the bulbocavernosus (SNB) after stimulation of the SNB axons in the BC motor nerve. The suppression occurred at 6- to 35-ms intervals between shocks to pudendal sensory nerve and BC motor nerve, and was markedly smaller in castrated males than in the other two groups. In contrast, a conditioning pulse to the contralateral BC motor nerve had no effect on the SNB antidromic field potential. These results indicate that androgen modulates the efficacy of synaptic transmission onto SNB motoneurons or other neurons involved in the BC reflex.
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  • 68
    ISSN: 1432-1106
    Keywords: In vivo voltammetry ; Somatostatin ; Growth harmone ; Dopamine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of growth hormone (GH) and somatomedin C (SmC), as well as those of apomorphine, dopamine (DA) agonist, or haloperidol (DA antagonist), upon the size of striatal voltammetric peaks 2 and 5 were investigated. Local intrastriatal injections of GH or SmC were followed by an increase in the height of both peak 2 (corresponding to the oxidation of extracellular dihydro-phenylacetic acid, DOPAC, a metabolite of DA) and peak 5 (which may represent the oxidation of striatal extracellular somatostatin, SRIF). Treatment with haloperidol also increased the size of the striatal catechol peak but was responsible for a reduction of the neuropeptidergic signal. By contrast, apomorphine determined a decrease in striatal peak 2 (DOPAC) while increasing the levels of peak 5 (SRIF). The data further support the chemical identification of peak 5 at +800 mV as related to the in vivo oxidation of SRIF; in addition they indicate the presence of a functional relationship between this neuropeptide and the GH and DA systems in the striatum of anaesthetised rats.
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  • 69
    ISSN: 1432-1106
    Keywords: Drug uptake ; Brain capillary endothelial cells ; Tumor cell membrane ; 9L glioma ; P-glyco-protein ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two weeks after the inoculation of 1.5 × 105 9L glioma cells into the rat brain, the uptake of radiolabelled drugs into the brain and the experimental 9L glioma during the first cerebral circulation was measured with a liquid scintillation counter and analyzed by the method of Oldendorf (1970). The expression of P-glycoprotein, which is known to be associated with the efflux of drugs, was also studied, using anti-P-glycoprotein monoclonal antibody, C-219. Furthermore, the ultrastructure of brain capillaries, tumor vessels, and glioma cells was studied by conventional and immunoelectron microscopy. Sucrose (control), the transport of which through the blood-brain barrier is known to be negligible, accumulated to fivefold higher levels in the tumor than in normal brain. Ranimustine (MCNU), 5-fluorouracil (5-FU), and doxorubicin showed little accumulation in the normal brain, whereas nimustine (ACNU) showed an increased accumulation. MCNU and doxorubicin showed negligible accumulation in the glioma cells despite diffusion into the tumor interstitial space. In contrast, ACNU and 5-FU showed an increased accumulation in tumor cells. The accumulation of 5-FU in the cultured 9L glioma cells was decreased by ATP inhibitors or by low temperature. Although both brain capillary endothelial cells and glioma cell membrane were immunohisto-chemically positive for P-glycoprotein, the tumor vasculature showed low expression of P-glycoprotein. The endothelial cells of tumor vessels ultrastructurally showed increased fenestrations, swelling, and disrupted junctions. Accordingly, it is suggested that hydrophobic drugs such as doxorubicin, being pumped out by P-glycoprotein, do not accumulate in 9L glioma cells as do other lipophilic drugs such as ACNU, or drugs such as 5-FU, which accumulate by a carrier-mediated mechanism.
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  • 70
    ISSN: 1432-1106
    Keywords: Neurodegeneration ; Striatum ; Substantia nigra ; Immunoblot ; Glial fibrillary acidic protein messenger RNA ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Following injection of 6-hydroxydopamine (6OHDA) into one side of the substantia nigra, immunohistochemical studies showed that the number of glial fibrillary acidic protein-positive [GFAP(+)] astrocytes in the striatum was significantly increased 1 day later and reached a maximum value, with intense immunoreactivity, 4 days after 6-OHDA injection. The number of GFAP(+) cells then gradually declined but was still 1.7 times the control value by 28 days postlesion. GFAP content, determined by immunoblot, and GFAP messenger RNA (mRNA) both reached maximal increases in the striatum 7 days after lesion: the mRNA returned to control values by 28 days, whereas GFAP content remained significantly elevated. Although the increases were all larger on the lesioned side, there were also significant changes on the contralateral side, as well as following saline injection. These results support the hypothesis that products released from damaged neurons are responsible for the induction of reactive gliosis, but cannot distinguish between effects mediated directly on the astrocytes or indirectly via other cells such as the microglia.
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  • 71
    ISSN: 1432-1106
    Keywords: Fornix lesion ; Spatial learning ; β receptors ; α2 receptors ; Locus coeruleus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous experiments revealed that the cholinergic deficit in rats with a partial fornix section was accompanied by an increase in turnover of noradrenaline (NE) in the hippocampus. This noradrenergic hyperactivity contributed to the cognitive deficit in lesioned rats, probably by interaction with the cholinergic system. The present experiment examines the reorganization of the noradrenergic system after the damage induced by partial fornix section and attempts to determine if the increase in NE turnover is of locus coeruleus (LC) origin, or if it is a result of local regulation at the noradrenergic terminals. Rats were submitted to knife-cut section of the fornix, resulting in a decrease in choline acetyltransferase activity in the hippocampus, correlated with a significant behavioral deficit in a spatial memory task. Lesioned rats learned a nonspatial memory task normally. Sections of brains of these rats were submitted to quantitative autoradiography. [125I]Iodopindolol binding was assessed in the dorsal and ventral hippocampus to determine availability of β receptors. This was found to be significantly lower in lesioned rats. [125I]Iodoclonidine was used to determine α2 receptors binding in dorsal and ventral hippocampus and in LC. There was no difference in α2 receptors in LC, a significant decrease in dorsal regions of the hippocampus, and a significant increase in ventral regions. Muscarinic M1 receptors in the hippocampus showed no changes after the lesion.
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  • 72
    ISSN: 1432-1106
    Keywords: Hippocampus ; Fluorocitrate ; Field potentials ; Glutamate ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fluorocitrate inhibits the glial tricarboxylic acid cycle and thereby the synthesis of glutamine, which is the main precursor for transmitter glutamate. We investigated the possibility that there is a functional correlate to fluorocitrate action by recording evoked field potentials in rat hippocampal slices. The excitatory postsynaptic potential (field-EPSP) was markedly depressed after 7–8 h of fluorocitrate action. The population spike was also reduced, but a major part of the reduction may be the result of weaker synaptic activation rather than reduced excitability of the postsynaptic cells. The activity of thin unmyelinated fibres was only slightly affected. Preceding the changes in the field-EPSP there was a decrease in the glutamine content in the fluorocitrate treated slices relative to controls. Only a small decrease in tissue glutamate was seen concomitantly with the synaptic failure, probably because the transmitter pool of glutamate in those fibres stimulated makes little contribution to the total tissue glutamate.
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  • 73
    ISSN: 1432-1106
    Keywords: Axotomy ; Retrograde tracing ; Spinal cord ; Motoneurons ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The content of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) in motoneurons was studied in four motor pools supplying muscles in the rat hind limb subserving different types of motor activity. The motor pools were identified by retrograde labeling with horseradish peroxidase or fluorophore-conjugated dextran amines, which were injected into the soleus, tibialis anterior, lateral gastrocnemius, or abductor digiti minimi muscles. After processing for immunohistochemistry, a semiquantitative evaluation was carried out to estimate the proportion of strongly, intermediately, and weakly labeled motoneurons, as well as motoneurons totally lacking CGRP staining. This revealed a considerable diversity in the intensity of CGRP labeling even for motoneurons in the same motoneuron pool. Thus, strongly labeled cells, as well as cells devoid of CGRP label, were found in all four motoneuron pools. However, a difference was found in the distribution of motoneurons innervating muscles with a dominant composition of fast and slow motor units, respectively, in that a larger fraction of the latter type lacked CGRP-LI. Moreover, generally motoneurons in the small motor units of the abductor digiti minimi muscle displayed weaker staining, and a larger proportion of cells was totally devoid of CGRP-LI (16%) compared with larger motor units of the other three muscles (1–10%). Small-sized cells within the γ-motoneuron size range were weakly stained or, more frequently, totally devoid of CGRP label (50%) as compared to larger cells, presumably representing α-motoneurons (1–16%). Five days after axotomy all four studied motoneuron pools displayed stronger CGRP labeling than corresponding unlesioned pools. However, a considerable variation in CGRP labeling persisted also among axotomized motoneurons. These results indicate that motoneurons normally display a great variation in CGRP-LI levels, but that motoneurons of small and slow-twitch motor units in general have lower levels than motoneurons of large and fast-twitch motor units, respectively. After axotomy, CGRP-LI increases in lesioned motoneuron pools compared with normal, but in a fraction of the axotomized motoneurons the increase seems to be discrete or even absent. The possible physiological implications of these findings are discussed.
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  • 74
    ISSN: 1432-1106
    Keywords: Septum-6-Hydroxydopamine ; Hypothalamus ; Mesencephalon ; Autophagous cytolyso somes ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the lateral septal area (LSA), both inhibitory and excitatory dopamine (DA) actions, as well as hypothalamic and midbrain DA efferents, have been described. Some neurons of the hypothalamic and midbrain DA systems contain somatostatin (SOM) or neurotensin (NT), and, in the LSA, the distribution of fibers containing these peptides overlaps with DA fibers. These data prompted us to test for the presence of SOM and NT in LSA dopaminergic axon terminals of hypothalamic and midbrain origins. To verify the origins of SOM and NT innervation of the LSA, the retrograde tracer horseradish peroxidase conjugated with wheat germ agglutinin (HRP-WGA) was injected into the LSA, and alternate brain sections were immunostained for SOM, NT, or tyrosine hydroxylase (TH) in group 1 rats. Numerous retrogradely labeled neurons were found immunopositive for SOM in the periventricular and basolateral hypothalamus, many HRP-WGA labeled cells contained NT immunoreactivity in the ventral tegmental area, and TH-immunoreactive retrogradely labeled neurons were observed in both brain areas. In a new approach, the presence of these peptides in dopaminergic boutons was assessed by combining peptide immunocytochemistry with acute 6-hydroxydopamine (6-OHDA) induced lesioning of DA cell groups. These groups of rats were treated with desipramine to protect the noradrenergic fibers, and 45 min later 1 μg 6-OHDA (in 0.5 μl saline) was unilaterally injected into the periventricular hypothalamus (group 2) or the ventral tegmental area (group 3). After 48 h the rats were killed and alternate septal sections of both groups were immunostained for TH, SOM, or NT. On the operated side of the LSA in both groups, electron microscopy revealed numerous axon terminals that were immunopositive for TH and contained autophagous cytolysosomes, an early sign of catecholamine fiber degeneration induced by 6-OHDA. In group 2, phagosomecontaining boutons were found immunopositive for SOM, but not for NT; vice versa, in group 3, only NT-positive degenerated boutons were detected. SOM and NT-positive degenerated axon terminals in both groups formed synaptic contacts with LSA neurons, in particular with somatospiny cells. On the contralateral side of the LSA, all of the axon terminals were intact. It has been shown that SOM exerts an inhibitory action, whereas NT has an excitatory effect on limbic area neurons. Thus, the results implicate that the differential peptide content of dopamine fibers marks their functional differences. It appears that LSA neurons receive double innervation from an inhibitory “somatostatinergic” DA system of the hypothalamus, and from an excitatory “neurotensinergic” DA system of the midbrain.
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  • 75
    ISSN: 1432-1106
    Keywords: Somatostatin ; Visual deprivation ; Cortical areas 17, 18, 18a ; Transience ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The distribution of somatostatin (SRIF)-immunoreactive neurons in the visual cortical areas 17, 18 and 18a of Wistar rats from birth to adulthood was followed in both normal and dark-reared animals. The SRIF neurons show difference in distribution amongst the three cortical areas studied as early as the first postnatal week. Area 17 was distinguished by fewer SRIF cells in the upper layers (I–III), which results in a lower overall density. The SRIF neurons in all areas appeared to increase in numbers up to about 3 weeks and then decline dramatically to adult levels, which were 14–19% of the peak levels. Although this decline was still obvious, it moderated to 25–31% in dark-reared animals. The greatest effect was seen in area 18 where, at 60 days of age, there were twice as many SRIF cells in darkreared as in normal controls. It is suggested that, under conditions of dark rearing, the overall pattern of development of SRIF neurons, being uninfluenced by extrinsic factors, reveals the cells' genetic potential.
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  • 76
    ISSN: 1432-1106
    Keywords: Antinociception ; Correlograms ; Rostral ventromedial medulla ; Ketamine-xylazine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anaesthetized rats, neurons located in the rostral ventromedial medulla (RVM) are classified by their differential responses to noxious stimulation. “On” cells are excited by noxious stimulation, “off” cells are inhibited and “neutral” cells are unaffected. Past research has primarily investigated the activity of these cells in lightly barbiturate anaesthetized animals while inducing a tail flick reflex. We recorded neuronal activity in the RVM of deeply ketamine-xylazine anaesthetized rats using a novel method of recording single- and multiunit activity simultaneously with one electrode. Under this anaesthetic paradigm we were able to record RVM cells which responded to noxious tail heating in the same manner as on and off cells without inducing a tail flick. A cross-correlogram analysis was done between the two levels of activity. It demonstrated that the RVM is a highly coordinated system in both the spontaneous period and the noxious evoked activity period. Through this technique it was also shown that both on and off cells fire simultaneously in the ketamine-xylazine paradigm.
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  • 77
    ISSN: 1432-1106
    Keywords: Dopaminergic transplants ; Amphetamine ; Sensitization ; Conditioning ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous treatment with amphetamine can influence the rotational response induced by amphetamine in rats with dopaminergic grafts. In order to distinguish whether this is due to graft “priming” or conditioning effects of the drug, groups of adult rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra, or with the lesion plus grafts of embryonic mesencephalic tissue in the striatum, were exposed to either: (1) amphetamine in the test environment and saline in the home cage; (2) saline in the test environment and amphetamine in the home cage; or (3) saline in the test environment and saline in the home cage. During this conditioning stage of the experiment, rats with the lesion alone rotated ipsilaterally and rats with the lesion plus grafts contralaterally when tested after administration of amphetamine. The rotation sensitized, i.e. the rats with lesions made more ipsilateral and the rats with grafts more contralateral turns, with repeated injections of the drug. On a subsequent no-drug test, only the rats with grafts which had previously experienced amphetamine in the test environment (1) showed conditioned contralateral rotation. Rats with grafts which had received the same number of amphetamine injections, but experienced the effects of the drug in the home cage (2), rotated ipsilaterally on the no-drug test to the same extent as rats with grafts which had received only saline (3). Thus, amphetamine treatment per se did not “prime” grafts. Rather, the response of the rats with grafts was the result of formation of a conditioned association between the amphetamine and the environment with which it had been paired. Also, there was no evidence for graft “priming” in subsequent tail-pinch and iced water rotation tests. Grafts reduced ipsilateral rotation in these tests, but the reduction was independent of prior treatment with amphetamine.
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  • 78
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    Experimental brain research 93 (1993), S. 55-65 
    ISSN: 1432-1106
    Keywords: Inhibition ; Dentate gyrus ; Hippocampus ; Behavioral state ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of two different waking behavioral states on the modulation of perforant, path-evoked population spikes were studied following prestimulation of either the perforant path itself, the dentate gyrus commissural/association pathway, or the medial septum. The intermediate-latency, post-inhibitory ‘rebound’ of the population spike, which normally follows short-latency, perforant path or commissure-induced inhibition, was substantially increased during forced locomotion on a treadmill, compared with quiet wakefulness. There was no effect of these behavioral states either on the short-latency inhibitory phase itself or on the average magnitude of the unconditioned population spike. The short-latency, GABA-mediated disinhibitory effect of medial septal prestimulation was slightly reduced by walking, as might be expected from the increased feedforward excitatory drive on hippocampal interneurons that occurs during walking. Septal prestimulation during walking also led to a large, intermediate-latency spike facilitation that was completely absent during the quiet, awake state. Lesions of the medial septum attenuated the effects of behavioral state on the post-inhibitory facilitation from both perforant path and commissural stimulation. Atropine reduced the walking-induced increase in intermediate-latency facilitation, but had no effect in the still condition. We conclude that, during walking, electrical stimulation within the hippocampal formation or septum leads to a delayed increase in dentate gyrus excitability that is probably mediated polysynaptically through the medial septum or fibers passing through it. This state dependency is not due to tonic suppression of the inhibitory systems within the dentate gyrus itself.
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  • 79
    ISSN: 1432-1106
    Keywords: Trigeminal ganglion ; Trigeminal nuclei ; Substance P ; Calcitonin gene-related peptide ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Employing a combination of fluorescent retro grade double labelling and immunofluorescence histo chemistry for substance P (SP) and calcitonin gene-relat ed peptide (CGRP), we examined collateral projections from single neurons in the trigeminal ganglion (TG) of the rat to both the principal sensory trigeminal nucleus (Vp) and the oral, interpolar or caudal subnuclei of the spinal trigeminal nucleus (Vo, Vi or Vc). In the rats that were unilaterally injected with fast blue (FB) into the Vp and with diamidino yellow (DY) into the Vo, Vi or Vc, neurons labelled with FB and/or DY were observed in the TG ipsilateral to the injections. Of the labelled TG neurons, about 2% were double labelled with both trac ers in the rats that were injected with FB into the Vp and with DY into the Vo or Vi, and about 10% were double labelled in the rats that were injected with FB into the Vp and with DY into the Vc. The results indicate that TG neurons sending their axons to the Vp project, by way of axon collaterals, to the Vc more frequently than to the Vo or Vi. Some of the TG neurons double labelled with FB and DY exhibited SP-or CGRP-like immunoreactivity (LI): Of the TG neurons that were double labelled with FB injected into the Vp and with DY injected into the Vo, Vi or Vc, about 38%, 49% and 42%, respectively, displayed SP-LI, and about 54%, 58% and 59%, respectively, showed CGRP-LI. Some of the SP-or CGRP-LI TG neurons that were double labelled with FB and DY were assumed to mediate pain signals to both the Vp and the spinal trigeminal nucleus (Vo, Vi and/or Vc) by way of axon collaterals.
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  • 80
    ISSN: 1432-1106
    Keywords: Dopamine ; Substantia nigra ; Striatum ; Hemitransection ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied the ability of the vigilance-promoting drug modafinil to modulate the anterograde and retrograde changes in tyrosine hydroxylase (TH) immunoreactivity and in dopamine (DA) stores in the nigro-neostriatal DA neurons, following a partial hemitransection of this ascending DA system, using a combined morphometrical, biochemical and behavioural analysis. Modafinil was given daily i.p. in doses of 10–100 mg/kg, starting 15 min after the lesion, and the partially hemitransected rats were killed 2 weeks later. Changes in TH-immunoreactive nerve cell bodies and nerve terminals induced by the partial hemitransection were studied in the substantia nigra and neostriatum in combination with image analysis. The substantia nigra and neostriatum were also subjected to biochemical analysis of DA, 3,4-dihydroxyphenylacetic acid and homovanillic acid levels. Modafinil treatment dose-dependently (10–100 mg/kg) counteracted the hemitransection-induced disappearance of nigral TH-immunoreactive nerve cell body profiles and neostriatal TH-immunoreactive nerve terminal profiles. A 2-week treatment with 100 mg/kg of modafinil also counteracted the hemitransection-induced depletion of DA stores in the neostriatum and the ventral midbrain. Moreover, the repeated daily treatment with modafinil (100 mg/kg) protected against the hemitransection-induced disappearance of striatal 5-hydroxytryptamine, 5-hydroxyindoleacetic acid and noradrenaline levels. Striatal DA function was analysed by studying apomorphine-induced (1 mg/kg, s.c.) ipsilateral rotational behaviour 4 and 11 days after the operation. A marked dose-dependent reduction of ipsilateral rotational behaviour was demonstrated after the daily modafinil treatment in the partially hemitransected rats. In another model involving unilateral nigral microinjections of 6-hydroxydopamine, acute (one single dose) modafinil (100 mg/kg) did not affect the contralateral rotational behaviour induced by apomorphine (0.05 mg/kg s.c.), when given 30 min before the apomorphine. Taken together, morphological, neurochemical and behavioural evidence has been obtained that anterograde and retrograde changes induced in the DA stores and TH immunoreactivity of the nigro-neostriatal DA neurons by a partial hemitransection are counteracted by modafinil in a dose dependent way with 100 mg/kg producing a significant protective action against impairment of DA transmission. The results of this study open up the possibility that modafinil may protect against the anterograde and retrograde degeneration of nigrostriatal DA neurons seen after mechanically induced injury.
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  • 81
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    Experimental brain research 97 (1993), S. 209-224 
    ISSN: 1432-1106
    Keywords: Hypoxia ; Neocortical slice ; Synaptic transmission ; GABAergic inhibition ; Interneurons ; Development ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To analyze the functional consequences of hypoxia on the efficacy of intracortical inhibitory mechanisms mediated by gamma-aminobutyric acid (GABA), extra- and intracellular recordings were obtained from rat primary somatosensory cortex in vitro. Hypoxia, induced by transient N2 aeration, caused a decrease in stimulus-evoked inhibitory postsynaptic potentials (IPSPs), followed by a pronounced anoxic depolarization. Upon reoxygenation, the fast (f-) and long-latency (l-) IPSP showed a positive shift in the reversal potential by 24.4 and 14.9 mV, respectively. The peak conductance of the f-and l-IPSP was reversibly reduced in the postanoxic period by 72% and 94%, respectively. Extracellular field potential recordings and application of a paired-pulse inhibition protocol confirmed the enhanced sensitivity of inhibitory synaptic transmission for transient oxygen deprivation. Intracellular recordings from morphologically or electrophysiologically identified interneurons did not reveal any enhanced susceptibility for hypoxia as compared to pyramidal cells, suggesting that inhibitory neurons are not selectively impaired in their functional properties. Intracellularly recorded spontaneous IPSPs were transiently augmented in the postanoxic period, indicating that presynaptic GABA release was not suppressed. Developmental studies in adult (older than postnatal day 28), juvenile (P14–18), and young (P5-8) neocortical slices revealed a prominent functional resistance of immature tissue for hypoxia. In comparison with adult cortex, the hypoxia-induced reduction in excitatory and inhibitory synaptic transmission was significantly smaller in immature cortex. Our data indicate a hypoxia-induced distinct reduction of postsynaptic GABAergic mechanisms, leading to the manifestation of intracortical hyperexcitability as a possible functional consequence.
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  • 82
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    Experimental brain research 97 (1993), S. 225-232 
    ISSN: 1432-1106
    Keywords: Alzheimer's disease ; Cortical layers ; Ibotenic acid ; Muscarinic receptor subtypes ; Nucleus basalis magnocellularis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The cholinergic system in the central nervous system is an important component of the neural circuitry of learning, memory and cognition. A decline of cholinergic innervation in the human brain is a characteristic feature of dementia of Alzheimer's type. In this study, changes in cholinergic markers were studied after a unilateral lesion of the nucleus basalis magnocellularis (nbM). Acetylcholinesterase (AChE) histochemistry showed a loss of cortical AChE-containing neurons, and choline acetyltransferase (ChAT) immunohistochemistry demonstrated a loss of cholinergic cells in nbM. The localizations of muscarinic Ml and M2 receptors using [3H]pirenzepine ([3H]PZ) and [3H]AF-DX 384, respectively, were studied by quantitative autoradiography 1, 2, 4 and 6 weeks following unilateral ibotenic acid lesion of nbM. A significant decrease in [3H]PZ binding sites was observed at postlesion week 1 in the parietal and temporal cortices. The decrease in [3H]AF-DX 384 binding sites on the lesioned side was observed throughout frontal, parietal and temporal cortices after postlesion week 1, with a significant increase after 6 weeks, possibly as result of loss of presynaptic receptors and upregulation of postsynaptic ones. Moreover, laminar distribution after nbM lesion shows that M1 and M2 receptor binding sites are more affected in superficial layers (I,II,III) than in the deep layers (IV,V,VI), depending on ligand, postlesion period and cortical region. Furthermore, nbM lesion causes a higher deficit of M2 receptors than of M1 receptors. These data suggest the existence of a presynaptic population as well as a postsynaptic population of M1 and M2 receptors which are differently affected after unilateral nbM lesion.
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  • 83
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    Experimental brain research 97 (1993), S. 301-304 
    ISSN: 1432-1106
    Keywords: Fictive locomotion ; Lateral hypothalamic area ; Mesencephalic locomotor region ; Hindlimbs ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In immobilized adult thalamic rats, electrical stimulation of sites within the lateral hypothalamic area (LHA) or the mesencephalic locomotor region (MLR) were found to elicit fictive locomotor patterns in hindlimb muscle nerves. Significant differences were found between several characteristics (average cycle period, locomotor episode duration, intralimb and interlimb coordination patterns) of the LHA-induced and MLR-induced fictive locomotor activities. These findings support the hypothesis that LHA and MLR play different functional roles during locomotion.
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  • 84
    ISSN: 1432-1106
    Keywords: CA1 pyramidal neurons ; Na+ plateau potentials ; High threshold Ca2+ spikes ; Persistent Na+conductance ; Theta rhythm ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The mechanisms mediating intrinsic and entrained CA1 pyramidal neuron rhythmic membrane potential oscillations were investigated in rat hippocampal slices. Intrinsic oscillations (6–14 Hz, 〈 10 mV) were evoked by long duration (2 s), depolarizing current pulses in 42% of the cells. Oscillations were also evoked by imposing sinusoidal transmembrane currents at 2, 7, and 14 Hz, adjusted at 7 Hz to imitate the synaptically mediated in vivo “intracellular theta”. Slow all-or-none events (40 mV, 55 ms) — reminiscent of the rhythmic, high threshold slow spikes observed in vivo — were evoked and entrained by the sine wave current cycles with large, imposed depolarization in 35% of the cells. Intrinsic oscillations were insensitive to Ca2+-free, Co2+ (2 mM) and Mn2+ (2 mM) solutions, but were blocked by tetrodotoxin (TTX; 5 μM), illustrating that they were Na+-mediated. Tetraethylammonium (TEA; 15 mM) unmasked slow all-or-none events (40–50 mV, 20–55 ms) and plateau potentials (40–60 mV, 100–700 ms). Plateaus were Co2+ and Mn2+ resistant and were abolished by TTX, hence suggesting that the underlying persistent conductance was Na+-mediated. Plateaus were entrained one-to-one at all sinusoidal current frequencies in Ca2+-free, TEA+Co2+, or TEA+Mn2+ solutions. However, the high threshold Ca2+ spikes uncovered in TEA+TTX could only follow sinusoidal currents of less than 7 Hz. In conclusion, the high threshold Ca2+ and persistent Na+ conductances coexist in CA1 pyramidal cells. The persistent Na+ conductance mediated the intrinsic oscillations, and fluctuated at all the sine wave current frequencies used. The more sluggish high-threshold Ca2+ conductance exclusively oscillated at frequencies of less than 7 Hz and did not support the intrinsic rhythm. Therefore, the findings suggest that the Na+-mediated oscillations may contribute to the high-frequency, type I, hippocampal theta rhythm present in vivo, whereas the high threshold Ca2+ conductance may take part in the low-frequency, type II rhythm.
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  • 85
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    Experimental brain research 94 (1993), S. 357-362 
    ISSN: 1432-1106
    Keywords: Transplantation ; Substantia nigra ; Host projections ; Striatum ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously reported that few striatal axons from adult host brain innervate intrastriatal grafts of fetal ventral mesencephalic tissue. To see whether the immature rat brain would favor striatal innervation of the graft, unilateral implantation of fetal ventral mesencephalic tissue was carried out at 7 (P7), 14 (P14), or 60 (adults) days of age in neonatally dopamine- (DA)-lesioned and nonlesioned rats. Immunocytochemistry for tyrosine hydroxylase (TH), and/or dopamine- and adenosine 3′,5′-monophosphate-regulated phosphoprotein-32 (DARPP-32) was performed 2–6 months later. In the great majority of immature and in all adult recipients, the resulting graft consisted of a distinct intrastriatal mass of tissue surrounded by the host parenchyma. Most TH-immunopositive neurons were found within the confines of such grafts, although some were lying at short distances into the host striatal tissue, particularly in immature recipients. In a few immature recipients, there was, however, extensive intermingling of TH-positive neurons with the adjacent host brain tissue. In all recipients grafted at P7, P14, or as adults, the distinct, intra-parenchymal grafts contained moderate numbers of DARPP-32-positive processes, mainly at their periphery. These results indicate that the limited capacity of host striatal neurons to grow axons into transplanted fetal ventral mesencephalic tissue is not markedly different in young versus adult rats. A better integration of the ventral mesencephalic graft into the striatal circuitry of immature — as opposed to adult — recipients should therefore rely more on the higher tendency of DA neurons to become located into the host tissue following transplantation in young rats.
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  • 86
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    Experimental brain research 96 (1993), S. 304-318 
    ISSN: 1432-1106
    Keywords: Hippocampus ; Subiculum ; Electrophysiology ; Glutamate ; GABA ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study determined the membrane and synaptic properties of neurons in the rat subiculum. Using the in vitro hippocampal slice preparation, intracellular recordings were obtained from 91 subicular neurons. Membrane properties and morphological characteristics were similar to those reported for hippocampal pyramidal neurons. Two categories of subicular neurons were distinguished based on their response to a depolarizing current pulse. One type of neuron showed bursting behavior and the second type was characterized as regular firing. Analysis of the charging functions during hyperpolarizing current pulses yielded a mean τ0 and τ1 for subicular neurons of about 13 ms and 0.60 ms, respectively. Using the model of an equivalent cylinder, the mean dendrite-to-soma conductance ratio (ρ) was estimated at 6.0 and electrotonic length constant (L) at 0.7. There was no difference in these values between bursting and regular firing neurons. Tetrodotoxin-resistant potentials (presumed calcium hump/spike) were evoked from bursting subicular neurons at lower current intensities than CA1 pyramidal neurons. Calcium humps could only be evoked from about half the regular firing subicular neurons. Subicular cells showed an excitatory/inhibitory postsynaptic potential (EPSP/IPSP) sequence in response to electrical stimulation in different layers of the CA1 area. An EPSP could also be evoked from stimulation of the superficial or deep layers of the presubiculum and was attributed to activation of entorhinal fibers of passage. At high stimulation intensity, an antidromic spike was often evoked following stimulation in the presubicular area or CA1 alveus. The evoked EPSPs were blocked by addition of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) to the bathing medium. In magnesium-free, CN-QX bathing solution, a longer lasting depolarization was recorded; this response was blocked by application of a N-methyl-d-aspartate (NMDA) receptor antagonist (AP5). Iontophoretic application of glutamate or quisqualate (10 mM) along the soma-dendritic axis of subicular neurons leads to either a short-latency depolarization or a burst of action potentials. Application of 10 mM GABA near the recording site usually produced a hyperpolarization, which, at times, was mixed with a depolarization. Mixed hyperpolarizing/depolarizing responses were observed when GABA was applied to the basal or apical dendritic areas. There were no significant differences in the synaptic properties or responses to drug application between bursting and regular firing neurons. These results indicate that subicular neurons (1) are composed of a heterogeneous population of cell types, (2) have similar electrical properties to other hippocampal principal neurons, (3) receive glutaminergic synapses from CA1 and entorhinal cortical neurons, (4) project to the presubicular area and fornix (via the alveus), (5) are inhibited by local circuit neurons, and (6) display complex responses to GABA.
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  • 87
    ISSN: 1432-1106
    Keywords: Ischaemia ; Hippocampal damage ; Microdialysis ; Glutamate ; Immunocytochemistry ; Amino acid neurotransmitters ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The redistribution of neurotransmitter amino acids resulting from 20 min of ischaemia was studied in the rat hippocampus by quantitative, electron microscopic immunocytochemistry and by in vivo microdialysis. Changes in the distribution of glutamate, glutamine, aspartate and GABA in various cell compartments of CA1 were analysed immediately after ischaemia or after 60 min of reperfusion, by incubating ultrathin sections with antisera raised against protein glutaraldehyde conjugates of the respective amino acids and subsequently with a secondary antibody coupled to colloidal gold particles. Transverse microdialysis probes coupled with HPLC and implanted in the same animals were used to determine the extracellular concentration of amino acids in the left hippocampus and to apply a drug (BW 1003C87) believed to modify the extracellular release of amino acids induced by ischaemia. Forebrain ischaemia was induced by temporary occlusion of the common carotid arteries in rats with permanently occluded vertebral arteries. The extracellular concentrations of glutamate, aspartate and GABA increased markedly during ischaemia, but returned rapidly to normal during reperfusion. BW 1003C87 (250 μM, in the dialysis fluid) did not modify the increase in extracellular concentration of amino acids during ischaemia. Glutamate-like immunoreactivity was reduced in pyramidal cell somata both immediately after ischaemia and after 60 min of reperfusion. This reduction appeared to be somewhat less pronounced for cells in the left hemisphere (perfused with BW 1003C87) than in the contralateral hemisphere. Ischaemia caused no consistent changes in terminals. The ratio between the intracellular levels of glutamate and glutamine was assessed by double-labelling immunocytochemistry, using two different gold particle sizes. The glutamate-glutamine ratio in glial cells was greatly increased after ischaemia, but recovered to a normal level within 1 h of reperfusion. Aspartate-like immunoreactivity was substantially reduced in pyramidal cell somata both immediately and 60 min after ischaemia, while profiles that were immunopositive for GABA in control brains showed increased GABA immunolabelling. These results suggest that postsynaptic neuronal elements as well as glial cells contribute to the extracellular overflow of excitatory amino acids during an ischaemic event: post-synaptic elements by leaking or releasing glutamate and aspartate, and glial cells by losing their ability to convert glutamate to glutamine effectively. The temporal association between the changes in the glial contents of glutamate and glutamine, and the extracellular amino acid fluctuations recorded by microdialysis in the same animals, underline the strategic role of glia in regulating the extracellular level of glutamate.
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  • 88
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    Experimental brain research 96 (1993), S. 419-429 
    ISSN: 1432-1106
    Keywords: Nucleus pontis oralis ; Pedunculopontine tegmental nucleus ; Hippocampal theta rhythm ; Carbachol ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of brainstem microinjections of carbachol on the hippocampal theta rhythm were examined in urethane anesthetized rats. The two most effective theta-eliciting sites with carbachol were the nucleus pontis oralis (RPO) and the acetylcholine-containing pedunculopontine tegmental nucleus (PPT) of the dorsolateral pontine tegmentum. RPO injections generated theta at mean latencies of 38.5±70.8 s and for mean durations of 12.9±5.1 min. Five of seven RPO injections gave rise to theta virtually instantaneously, i.e., before the completion of the injection. PPT injections generated theta at mean latencies of 1.7±1.1 min and for mean durations of 11.9±6.0 min. Injections rostral or caudal to RPO in the caudal midbrain reticular formation (RF) or the caudal pontine RF (nucleus pontis caudalis) generated theta at considerably longer latencies (generally greater than 5 min) or were without effect. Medullary RF injections essentially failed to alter the hippocampal EEG. The finding that theta was produced at very short latencies at RPO suggests that RPO, the putative brainstem source for the generation of theta, is modulated by a cholinergic input. The further demonstration that theta was also very effectively elicited with PPT injections suggests this acetylcholine-containing nucleus of the dorsolateral pons may be a primary source of cholinergic input to RPO in the generation of theta. The hippocampal theta rhythm is a major event of REM sleep. The present results are consistent with earlier work showing that each of the other major events of REM sleep, as well as the REM state, are cholinergically activated at the level of the pontine tegmentum.
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  • 89
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    Experimental brain research 96 (1993), S. 473-479 
    ISSN: 1432-1106
    Keywords: Spinal cord ; Proprioceptive afferents ; GpIa afferents ; Central pattern generator ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It had been shown previously that, following spinalization of the neonatal rat on postnatal day 7 (PN7), at the middle thoracic level, there was spontaneous recovery of coordinated stepping in the hindlimbs, enabling the animal to execute quadrupedal locomotion, with an ataxic gait. No significant recovery occurred in rats that were similarly spinalized on PN14. Despite the functional recovery in the PN7 group, their hindlimbs were paralyzed when not in contact with a surface. In the present experiments, at 16–18 weeks after spinalization, muscle spindle GpIa and cutaneous afferents were tested for functional connectivity to the alpha motoneurons (a-MNs) that innervate the right triceps surae (TS) muscles. The Hoffmann reflex (H-reflex), the tonic stretch reflex (TSR), and cutaneous reflexes were recorded from the right TS muscles in the nonanesthetized, intercollicular decerebrate preparation. The H-reflex and the TSR were readily elicited from the PN7 animals, but not from the PN14 animals. The PN14 preparations were characterized by prolonged (〉 18 h in 3/8 cases), spontaneous discharge of motor units, and prominent M responses. There was widespread, bilateral convergence of cutaneous afferents from the hindquarters to the a-MNs of the TS muscles in both the PN7 and the PN14 preparations. In the nonspinalized, control preparation, only ipsilateral, cutaneous afferents activated the right TS a-MNs. These results demonstrate that in the chronic (〉 3 months after spinalization), spinalized PN7 rat, but not in the PN14 rat, there is a tight functional connectivity between the hindlimb GpIa afferents and their homonymous a-MNs.
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  • 90
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    Experimental brain research 96 (1993), S. 480-486 
    ISSN: 1432-1106
    Keywords: Neocortical transplantation ; Axonal tracing ; Adult ; NMDA ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fetal neocortical block grafts placed into new-born recipients are able to exchange axonal projections with the host central nervous system, as shown in several previous experiments. The present study examined the connectivity of fetal neocortical block transplants placed into the excitotoxically ablated cortex of adult rats. Young adult rats received injections of the excitotoxic amino acid N-methyl-D-aspartate into the sensorimotor cortex area 1 week prior to receiving a fetal (E14–15) neocortical transplant. Afferent and efferent connections of these grafts were examined 3–6 months after transplantation by injecting the transplants with the fluorescent retrograde tracers fast blue and diamidino yellow or with the anterograde tracer Phaseolus vulgaris leucoagglutinin. Retrogradely labeled neurons were observed within several host brain regions including the ipsilateral neocortex, several thalamic nuclei, subcortical areas such as claustrum and lateral hypothalamus, nucleus basalis, dorsal raphe nuclei and locus coeruleus. Fibers labeled with Phaseolus vulgaris leucoagglutinin were found extending throughout the transplants, but with rare exceptions fibers were not observed within the host brain. The experiments showed that neocortical block grafts placed into the excitotoxically ablated neocortex receive afferent input from areas in the host brain that normally innervate the sensorimotor cortex. The extensive Phaseolus vulgaris leucoagglutinin-positive axonal labeling found within the grafts demonstrated the ability of the grafted neurons to establish extensive intrinsic graft connections. Their failure to project out of the grafts suggests that the mature host brain does not provide a permissive environment for neurite extension.
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  • 91
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    Experimental brain research 92 (1993), S. 351-359 
    ISSN: 1432-1106
    Keywords: Vestibular nuclei ; Locus coeruleus ; Dopamine β -hydroxylase ; Tyrosine hydroxylase ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study describes a regionally selective projection of tyrosine hydroxylase and dopamine β -hydroxylase-immunoreactive fibers from locus coeruleus (LC) and the A4 region of nucleus subcoeruleus to the vestibular nuclear complex in Long-Evans and Sprague-Dawley rats. These fibers travel in two distinct pathways. A lateral descending noradrenergic bundle provides input from LC to the superior vestibular nucleus (SVN), the cochlear nuclei, and the cerebellar cortex. A medial descending noradrenergic bundle provides input to the lateral vestibular nucleus (LVN), medial vestibular nucleus (MVN), and the inferior vestibular nucleus (IVN) before continuing on to the cochlear and cerebellar nuclei. The terminal plexus of these fibers varies markedly across these vestibular nuclear regions. Immunoreactive axons form a dense plexus around somata and proximal dendrites of Deiters' neurons in dorsal LVN. The axon plexus is less dense in SVN and ventral LVN, and relatively sparse in MVN and IVN. This regional selectivity of noradrenergic innervation suggests that central adrenergic systems may selectively modulate vestibulospinal reflexes at the level of the vestibular nuclear complex.
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  • 92
    ISSN: 1432-1106
    Keywords: Extracellular recording ; Barrel field ; Somatosensory cortex ; Differential development ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Development of the barrel field in layer IV of SI cortex of neonatal rats was studied in vivo using electrophysiological recording techniques. This study was designed to determine (a) the earliest time SI cortex is responsive to peripheral mechanical and/or electrical stimulation and (b) whether the development of the SI cortical barrel field map of the body surface follows a differential pattern of development similar to the pattern previously demonstrated using peanut agglutinin (PNA) binding (McCandlish et al. 1989). Carbon fiber microelectrodes were used to record evoked responses from within the depth of the cortex in neonatal rats between postnatal day 1 (PND-1), defined as the day of birth, and PND-14. Evoked responses were first recorded approximately 12 h after birth. These responses in the youngest animals were of low amplitude, monophasic waveshape, and long latency, with long interstimulus intervals necessary to drive the cortex. Increases in amplitude and complexity of waveshape and decreases in latency were observed over subsequent postnatal days. The earliest responses recorded on middle PND-1 were evoked by stimulation of the face and/or mystacial vibrissae. The next responses were evoked approximately 24 h after birth (late PND-1) by stimulation of the forelimb. The last responses were evoked approximately 36 h after birth (middle PND-2), by stimulation of the hindlimb. The physiological map of the representation of the body surface follows a developmental gradient similar to the gradient observed using PNA histochemistry; however, the lectin-generated morphological map lagged approximately 48 h behind the physiological map. The representation of the body surface appears to be topographically organized as early as PND-2. Our results suggest that thalamocortical afferents have reached the developing cortical plate and are functional before glial cells are first detected. These results do not sit well with a theory of barrel field development based entirely on the role of glia in pattern formation.
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  • 93
    ISSN: 1432-1106
    Keywords: Inflammation ; Muscle pain ; Slowly conducting muscle afferents ; Sensitization ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anaesthetized rats, the influence of an experimental inflammation and of acetylsalicylic acid (ASA) on the discharge properties of muscle receptors with slowly conducting afferent fibres was studied using a single-fibre recording technique. Following the induction of a myositis with carrageenan, the proportion of units having background activity and the frequency of the background discharge were significantly increased. The latter change was particularly prominent in high-threshold mechanosensitive (HTM) units. There was evidence for an inflammation-induced lowering of mechanical threshold in HTM units, but the change was not statistically significant. Administration of ASA intravenously led to a decrease in the frequency of background discharge in some units while others were unaffected, although they appeared to be sensitized by the inflammation. If one assumes that at least some of the HTM receptors fulfil nociceptive functions, the results suggest that the pain and tenderness of an inflamed muscle is largely due to a sensitization and hence increased activity of nociceptive muscle receptors. The sensitization is only partially abolished by ASA.
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  • 94
    ISSN: 1432-1106
    Keywords: Chromaffin cell ; Neurite outgrowth ; Substance P ; Neurokinin A ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rat chromaffin cells display phenotypic plasticity postnatally. In the presence of glucocorticoids, they retain a chromaffin cell phenotype, whilst in the presence of nerve growth factor and the absence of glucocorticoids they adopt a sympathetic neuronal phenotype. The tachykinins have some of the characteristics of a neurotrophic factor and are present in the form of a substance P afferent input in the rat adrenal medulla. We investigated the effects of stable NK1 and NK2 tachykinin receptor agonists, Ava[L-Pro,N-Me-Leu-10]SP7-11 (GR73632) and [Lys-3,Gly-8,R-Lac-Leu-9]NKA3-10 (GR64349), respectively, on the survival and phenotype of P5-7 rat chromaffin cells in vitro. GR73632 promoted neurite outgrowth, characteristic of the sympathetic neuronal phenotype, in the absence of NGF and glucocorticoids, but was without effect on survival after 2 weeks in culture. GR64349 was without effect.
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  • 95
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    Experimental brain research 92 (1993), S. 479-488 
    ISSN: 1432-1106
    Keywords: Development ; Muscle activity ; Locomotion ; Coordination ; Spectral analysis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The development of the electromyogram (EMG) of tibialis anterior (TA) and medial gastrocnemius (GM) during locomotion was studied in normal rats from the onset of quadruped walking (postnatal day 10, P10) until P42. The objectives were to relate signal properties of the EMG and coordination of muscle activity to functional development of the hindlimb, which proceeds rapidly around PI5. Both the EMG characteristics and the activation pattern showed marked changes with age. Initially, the EMG bursts were irregular and protracted. The activity level in the two muscles, in particular in GM, seemed to be low. Until P14, the motor units of GM showed a tendency towards synchronization. The EMG of TA consisted of an adult-like interference pattern from the youngest age studied. Although co-contraction of TA and GM was sometimes observed until P14, reciprocal activation of the muscles was evident at all ages. The timing of the alternating pattern became more accurate with age. The activity level in both muscles increased markedly from P15. These changes were reflected in the form factor (coefficient of variability) of the EMG and, to a lesser extent, in the power spectra. The time course of these changes bears a close temporal relationship to the development of locomotion. These results suggest that the degree of muscle activation is a decisive factor with respect to locomotor development. It is proposed that this is related to the maturation of supraspinal control.
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  • 96
    ISSN: 1432-1106
    Keywords: Blink reflex ; Nicotine ; Basal ganglia ; Orbicularis oculi ; Rat ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In humans and rats we found that nicotine transiently modifies the blink reflex. For blinks elicited by stimulation of the supraorbital branch of the trigeminal nerve, nicotine decreased the magnitude of the orbicularis oculi electromyogram (OOemg) and increased the latency of only the long-latency (R2) component. For blinks elicited by electrical stimulation of the cornea, nicotine decreased the magnitude and increased the latency of the single component of OOemg response. Since nicotine modified only one component of the supraorbitally elicited blink reflex, nicotine must act primarily on the central nervous system rather than at the muscle. The effects of nicotine could be caused by direct action on lower brainstem interneurons or indirectly by modulating descending systems impinging on blink interneurons. Since precollicular decerebration eliminated nicotine's effects on the blink reflex, nicotine must act through descending systems. Three lines of evidence suggest that nicotine affects the blink reflex through the basal ganglia by causing dopamine release in the striatum. First, stimulation of the substantia nigra mimicked the effects of nicotine on the blink reflex. Second, haloperidol, a dopamine (D2) receptor antagonist, blocked the effect of nicotine on the blink reflex. Third, apomorphine, a D2 receptor agonist, mimicked the effects of nicotine on the blink reflex.
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  • 97
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    Experimental brain research 93 (1993), S. 1-5 
    ISSN: 1432-1106
    Keywords: Complex-spike cell ; Theta cell ; Rhythmic slow activity ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The activity of hippocampal complex-spike cells (presumed pyramidal cells) and theta cells (presumed interneurons) was examined during transitions from non-theta electroencephalogram (EEG) states to theta EEG states in freely moving and sleeping rats. Theta cell firing rates were significantly depressed in a 1-s period centered on the EEG transition relative to the surrounding 1-s periods (normalized rates±SEM): 1.05±0.02 for the “non-theta” period, 0.59±0.03 for the “transition” period, and 1.36±0.04 for the “theta” period (n = 26 cells). Conversely, complex-spike cell firing was significantly increased during the transition period: 0.51±0.11 for the “non-theta” period, 2.24±0.19 for the “transition” period, and 0.24±0.04 for the “theta” period (n = 27 cells). This diametrically altered activity indicates that theta cells must be actively inhibited during the transition. The increased activity in complex-spike cells during the transition may be simply a release from inhibitory control by interneurons. The pattern of theta cell inhibition together with increased complex-spike cell activity appears to be a general property of transitions into the theta EEG state, irrespective of behavior. It is suggested that increased activity in septal afferents (GABAergic cell activity greater than cholinergic cell activity) initially inhibits hippocampal interneurons. The inhibition is not sustained because of an activity-dependent decrease in the potency of the septointerneuronal inhibition, leaving the rhythmic excitatory (cholinergic) septointerneuronal inputs, together with principal cell inputs, to increase interneuron firing rates.
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  • 98
    ISSN: 1432-1106
    Keywords: Horizontal cells ; Hippocampus ; Morphology ; Electrophysiological properties ; Development ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In an ontogenetic study, combining morphological analysis and patch clamp recordings, a transiently appearing horizontal cell type was identified in the dentate gyrus. The cells were exclusively located in the outer third of the stratum moleculare. They were present at postnatal day 2 (P2) and could be identified with fluorescent dyes until around P14. The morphology was bipolar, with a putative axonal and a dendritic process stretching out parallel to the pial surface without any preferential direction. Patch clamp studies in the current and voltage clamp mode were performed in hippocampal slices on visually identified horizontal cells, between P4 and P7, which were subsequently stained with lucifer yellow. The cells had a low resting membrane potential, around — 55 mV. They were excitable, displaying broad action potentials (duration 3–20 ms) and, unlike mature dentate granule cells, they also expressed a strong delayed inward rectifier with properties reminiscent of the IQ current. Unlike granule cells, no postsynaptic signals could be observed during elevation of [K+]o or electrical stimulation, suggesting that the horizontal cells did not participate in functional hippocampal circuitry. We suggest that these cells represent migrating cells with subsequent differentiation to granule cells or inhibitory interneurons. Alternatively they may be part of the early radial glia or serve as transient target cells for afferent fibres between the entorhinal cortex and the dentate gyrus.
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 94 (1993), S. 88-96 
    ISSN: 1432-1106
    Keywords: Basal ganglia ; Parkinson's disease ; Dopamine ; Substantia nigra ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The blink reflex abnormalities present in the 6 hydroxydopamine (6-OHDA) lesioned rat model of parkinsonism mimicked those of the human with Parkinon's disease. In alert rats, we monitored the long and short latency components of the orbicularis oculi electromyographic (OOemg) response evoked by electrical stimulation of the supraorbital branch of the trigeminal nerve (SO). Two paradigms, habituation and double pulse, provided a measure of blink reflex excitability. In normal rats, repeated stimulation of the SO produced habituation of the R2 component of the blink. In the double pulse paradigm, presentation of two identical SO stimuli resulted in a reduced or suppressed OOemg response to the second stimulus relative to the first. In rats with complete, unilateral lesions of midbrain dopamine neurons, repeated SO stimulation produced facilitation rather than habituation of the R2 component of the blink reflex. This facilitation occurred only with the eyelid contralateral to the lesion. In the double pulse paradigm, the lesioned rats showed increased excitability rather than suppression. This effect occurred bilaterally, although the increased excitability was strongest contralateral to the lesion. Rats with partial lesions of midbrain dopamine neurons exhibited qualitatively similar, but less pronounced blink reflex abnormalities. The R1 component of the blink reflex was unaffected by either the complete or partial lesions. Thus, modification of the blink reflex by 6-OHDA lesions provides a reproducible parkinsonian-like symptom which is amenable to investigations of increases in reflex excitability.
    Type of Medium: Electronic Resource
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  • 100
    ISSN: 1432-1106
    Keywords: Supraoptic nucleus ; U50,488 ; Naloxone ; Tolerance ; G-protein ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated the effects of intracerebroventricular (i.c.v.) pertussis toxin upon the sensitivity of supraoptic oxytocin neurones to intravenous morphine (1-5000 μg/kg) in urethane-anaesthetized rats. The maximal inhibitory capacity of morphine was diminished by prior administration of pertussis toxin. Some cells were tested with both morphine and with the kappa-opioid agonist U50,488 (1-5000 μg/kg): U50,488-induced inhibition of firing rate was apparently unimpaired by pertussis toxin pre-treatment. The opioid inhibition of firing rate seen in the absence of and after pertussis toxin pretreatment was naloxone-reversible. Thus a pertussis toxin-sensitive G protein may mediate the inhibitory action of morphine upon supraoptic putative oxytocin neurones or inputs to them.
    Type of Medium: Electronic Resource
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