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  • 1
    ISSN: 1432-1106
    Keywords: Catalepsy ; Electromyography ; GABA ; Limb rigidity ; Ventromedial thalamic nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cataleptic state induced by injection of the GABAmimetic drug muscimol into the rat's ventromedial thalamic nucleus (VM) was examined using an electromyographic (EMG) approach. Muscimol in doses up to 50 ng/0.5 μl injected into the VM induced a tonic EMG activity in the gastrocnemius muscle which is considered to be a measure of limb rigidity. This tonic EMG activity was found to be dose-dependent, GABA specific and locus specific. By recording EMG signals from chronically implanted electrodes in awake, unrestrained rats it was shown that muscular reactions serving to maintain the animal's static equilibrium were intact in the state of VM induced catalepsy. However, animals were unable to initiate movements or locomotion even when they were forced by strong external stimuli. It was found that the animals' immobility was due to an inability to induce a phasic activation of their muscles whereas tonic activation still occurred. It is concluded that (1) the rat's VM is part of a neuronal chain conducting information relevant for the expression of limb rigidity, (2) the VM is involved in the central mechanisms responsible for the phasic activation of a set of muscles.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 38 (1980), S. 109-114 
    ISSN: 1432-1106
    Keywords: Neuromuscular ; Reflexes ; Gait
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary If an obstacle impedes the forward swing of a cat's foot, the animal responds by rapidly lifting the foot over the obstacle. In freely moving cats, the electrical activity of hindlimb flexors and extensors was recorded during such reactions elicited both mechanically and electrically. The sequencing of muscle activity was more complex and longer in duration in the mechanically elicited reactions. Anaesthesia of the foot dorsum abolished responses in ankle extensors and knee flexors, and converted the responses of ankle flexors to simple stretch reflexes. Although our findings closely resemble those reported for chronic spinal kittens, there are interesting points of difference, which should be taken into account if the notion of a purely spinal mediation of the placing reaction during stepping is to be accepted.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 67 (1987), S. 216-219 
    ISSN: 1432-1106
    Keywords: Stepping automatism ; Locomotion ; Step cycle ; Guinea-pig ; SIS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary “Stepping automatism” has generally been studied in mesencephalic or spinal cats and has been induced electrically with the animal on a treadmill (Shik and Orlovsky 1976). Derivatives of 4-R-2,2,5,5-tetrakis (trifluoromethyl)-imidazoline (SIS = Substances capable of Inducing Stepping) I–IV (Liu 1985, Liu et al. 1984) can induce regular “stepping automatism” in guinea pigs. The present paper concerns the guinea-pig step cycle of the forelimb during SIS II-induced “stepping automatism” analysed with the use of X-ray cinematography and electromyography (EMG) studies in suspended animals. Results show that the flexion phase (F E1) and the extension phase (E2 E3) of the SIS-induced step cycle are quite comparable to those of the normal step cycle in other quadrupedal animals walking on the ground. The excursions of elbow, shoulder and scapula joints are all in phase in F and E3, whereas the scapula is largely out of phase with the elbow and shoulder during E1 and E2. It is surprising that during SIS II-induced locomotion in guinea pigs suspended in the air, “yield” could be seen in both, the elbow and the shoulder joints.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: GABA ; Motor pattern ; Motor performance ; Substantia nigra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to investigate the role of GABAergic neurotransmission within the reticular part of substantia nigra (SNR) in the switching of motor patterns and the performance of movements, cats trained to walk on the running belt of a treadmill at constant speed were subjected to three different tests: (1) a food dispenser test measuring the animals' capacity to switch motor patterns in order to get access to food during walking; (2) an obstacle test measuring the animals' capacity to switch motor patterns in reaction to incoming obstacles; (3) EMG recording of two representative antagonistic muscles of the hindlimb during walking on the treadmill. Local injection of a moderate dose of the GABA antagonist picrotoxin (PTX; 250–500 ng/0.5 μl) into the SNR disrupted the animals' capacity to switch motor patterns in the food dispenser test, but not in the obstacle test. These animals displayed normal EMG patterns during walking. Higher doses of intranigral injections of PTX, however, impaired the execution of movements per se as detected by an increased number of ‘faults’ in the obstacle test and pathological EMG patterns during walking. These experiments support the view that (1) the SNR plays a distinct role for switching motor patterns; (2) the SNR is involved in the control of movements per se; (3) the degree of motor disorder depends on the degree of pathology within this brain structure.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: δ-aminovaleric acid ; Baclofen ; GABAB antagonist ; Spasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The action of δ-aminovaleric acid (AVA) on the muscle relaxant properties of baclofen, a GABAB receptor agonist, was investigated in two experimental models: (1) the pathologically increased muscle tone of the gastrocnemius muscle in spastic mutant Han-Wistar rats and (2) the Hoffmann (H)-reflex recorded from plantar foot muscles after electrical stimulation of the tibial nerve in barbiturate (60 mg/kg) anaesthetized rats. In both paradigms coadministration of AVA (500 nmol/5 μl) antagonized the muscle relaxant action of intrathecally applied baclofen (0.2–2 nmol), but failed to affect the muscle relaxant effects of intrathecally injected muscimol (2–20 nmol). In contrast, coadministration of bicuculline (1 nmol) did block the muscle relaxant action of muscimol, but failed to alter the effects of baclofen. When administered alone, bicuculline (1 nmol), or AVA (500 nmol–2 μmol) were without intrinsic action in both paradigms. In an additional series of experiments we investigated the action of AVA on a supraspinal effect of baclofen. Coadministration of AVA (12.5 nmol/0.5 μl) in the ventromedial thalamic nucleus antagonized the catalepsy induced by baclofen (ED50 10 pmol/0.5 μl), as indicated by an increase in ED50 of baclofen by a factor of 4.835 and a parallel shift of the probit-log dosage regression line to the right. The parallel shift seems to be consistent with a competitive mechanism of action of AVA. This study presents evidence that AVA antagonizes central pharmacological actions of baclofen at both spinal and supraspinal sites without affecting the actions of a GABAA agonist, muscimol.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 5 (1993), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The re-expression of the developmentally regulated serine protease inhibitor glia-derived nexin (GDN) was investigated 1 year after transient global ischaemia induced by the four-vessel occlusion technique in rats. The CA1 sector of the hippocampus was severely shrunken due to the absence of pyramidal cells, but still clearly discernible due to the continued presence of the parvalbumin-containing GABAergic neurons. In this partially neuron-depleted hippocampus, GDN immunoreactivity was found in reactive astrocytes containing glial fibrillary acidic protein. GDN-positive astrocytes were also found in other lesioned areas, the reticular thalamic nucleus and the cerebellar cortex. Thus, the re-expression of GDN in the adult excitotoxically lesioned brain described previously in the gerbil model of ischaemia persists. The continued presence of the protease inhibitor might disturb the proteolytic balance and lead to the deposition of pathological breakdown products of proteins, e.g. β-amyloid.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1435-1463
    Keywords: Keywords: Oxidative stress, iron, cerebral oligemia, striatum, water maze, spatial orientation, lazaroids.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. Oligemic episodes and increased iron concentration have both been proposed as being involved in neurodegenerative diseases. In animal models, a combination of both of these might therefore mimic the clinical pathology in humans. In rats, intrastriatal injections of ferric chloride, FeCl3, one week after a 60-minute oligemic episode, produced by bilateral clamping of the carotid arteries under pentobarbital anaesthesia (BCCA) impaired the animals' learning ability in a water maze task. Median adult rats, after intrastriatal 0.3 μg FeCl3, are impaired when challenged during the first three trial blocks, while after 0.06 μg FeCl3, an impairment is seen during the process of habituation to the challenge. Two-year-old animals do not show any learning effect at all after the combination of BCCA and intrastriatal FeCl3. Lazaroid U-74389G, a potent inhibitor of iron-induced lipid peroxidation, totally prevents the learning impairments in both median adult and aged animals, suggesting that iron-induced lipid peroxidation may be responsible for the late learning deficiencies. However, when U-74389G is applied one week after the oligemic episode but without the additional injection of iron, U-74389G on its own also impairs the animals' learning ability. The present animal model, when applied to clinical studies of lazaroids in humans, does seem able to give reliable information concerning the neuroprotective properties of such drugs.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neural transmission 7 (1994), S. 47-59 
    ISSN: 1435-1463
    Keywords: Oligemia ; learning ; reference memory ; working memory ; hippocampus ; nucleus accumbens ; acetylcholine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats were subjected to 60 min of bilateral clamping of the carotid arteries (BCCA) in pentobarbital anaesthesia and tested in a hole board with 8 of the 25 holes baited with food pellets hidden in a serial order. All rats learned to recognize the pattern as a reference during an acquisition period at 2–14 days post surgery, i.e. reference memory. During the recall tests 29–37, 165–175 and 240–250 days later BCCA animals showed a decrease in memory revealing a significant increase in reference memory errors. The number of working memory errors, i.e. reexamination of inspected previously baited holes, did not differ from those of sham operated controls. The number of pellets eaten in serial order from hole 1 to hole 8 was significantly decreased in BCCA animals compared with controls, while the number of holes inspected by the animals in the two groups were the same. Thus the observed behaviour changes appear not to be caused by motor or motivation deficiencies.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neural transmission 87 (1992), S. 163-173 
    ISSN: 1435-1463
    Keywords: Catalepsy ; rotarod test ; muscarinic receptors ; carbachol ; nucleus ; reticularis thalami
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study investigated the functional relationship between the experimentally induced changes in the activity of the cholinergic, muscarinergic system of the rostral area of the nucleus reticularis thalami (TRN) and the motor behaviour. The effect of direct stimulation of the rostral TRN by the cholinergic agonist carbachol on the behaviour of freely moving rats was observed. Unilateral injection of carbachol (0.2–3.2 Μg/0.5 Μl) into the rostral TRN caused catalepsy which appeared rapidly and was short-lasting. Furthermore, it induced impairment of the performance on the rota rod. Both effects were dose-dependent. The cholinergic antagonist scopolamine (6.66 Μg) coadministered with the equimolar dose of carbachol (3.2 Μg) antagonized the effects of carbachol on both behavioural tests. The described effects seem to be cholinergic- and site-specific within the rostral TRN. The present results suggest that activation of the cholinergic, muscarinergic receptors in the rostral TRN modulate the motor function of rats.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1435-1463
    Keywords: GABA ; bicuculline ; seizure ; status epilepticus ; blood flow reduction ; cerebral protection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats were exposed for 24 min to bilateral clamping of the common carotid arteries (BCCA) in pentobarbital anaesthesia. The GABA content was measured 24 hours, 48 hours, 4 days, 14 days and 3 months after BCCA. In other groups of rats seizures were elicited by i.p. injection of (+)-bicuculline (3 mg/kg) 24 hours, 48 hours, 4 days, 14 days and 3 months after BCCA. Analysis of the GABA content revealed significant increase compared with controls in the hippocampus, frontal cortex and substantia nigra from 24 hours up to 3 months. Bicuculline treatment induced tonic/clonic seizures and status epilepticus in sham operated animals; these effects were drastically diminished at various time points after BCCA. The present results suggest that BCCA produces a longlasting increase in GABA content and as a consequence protection from bicuculline-induced seizures.
    Type of Medium: Electronic Resource
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