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Notes: Summary The effects of the calcium entry blockers verapamil (V), diltiazem (D), nifedipine (NF) and nicardipine (NC) have been studied on calcium concentration-effect curves elicited in depolarized (K+, 40 mmol/l) and in serotonin-exposed (6 μmol/l) rat middle cerebral arteries (RMCA) in order to compare the relative potencies of the blockers against these two calcium channel activating mechanisms. In control conditions, Ca2+ sensitivity expressed as pD2 and maximal active wall tension (AWT) were not significantly different in depolarized and in 5-HT-exposed vessels: pD2: 3.39 ±0.08 vs 3.50 ± 0.06 and AWT: 0.93 ± 0.15 mN · mm−1 vs 0.90 ± 0.16 mN · mm−1 respectively. V, D, NF and NC displaced Ca2+ control curves to the right and depressed the maximum contractile response in the two experimental conditions, which suggests a noncompetitive type of antagonism. All the blockers were more potent inhibitors of Ca2+-induced contractions in depolarized than in serotonin-exposed middle cerebral arteries. The IC50 values (concentration of blockers producing a 50% inhibition of maximal control contractile response) were (nmol/l) : V = 20, D = 120, NF = 0.4, NC = 1 and V = 400, D = 10000, NF = 20, NC = 7 in depolarized and serotonin-exposed arteries respectively. From these IC50 values, the relative order of potency of the CEB's was not the same in the two experimental conditions suggesting that while serotonin and K+ both promote the entry of Ca2+ into vascular smooth muscle cells of RMCA, they either activate a different gating mechanism associated with a single common channel or perhaps distinct channels. Comparison of the results obtained in this study for depolarized rat middle cerebral arteries with those previously obtained in depolarized rat mesenteric resistance arteries (RMRA) revealed that while Ca2+-induced contractile responses were inhibited in a similar non-competitive manner by the four CEB's, the respective IC50 values showed that potencies and rank of relative potency of the blockers were different in the two types of vessels. D and NC were equally potent in both preparations (IC50 ratio = 2.5 and 3 respectively) but RMCA were more sensitive to V and NF than RMRA (IC50 ratio = 6.5 and 11 respectively). These results are discussed and it is proposed that regional differencies in the conformation and/or the activation of the voltage-gated Ca2+ channels may exist in different vascular beds.

Notes: Summary The effect of unilateral sciatic nerve transection on behavioural responses produced by intrathecal administration of substance P (SP), neurokinin A, eledoisin and physalaemin was investigated in the rat. The injection of SP (3 nmol/rat) into the subarachnoid space was followed by reciprocal scratching, biting and licking of the fore- and hind-limbs. There was no observable difference in the behavioural response to SP between rats with nerve transection and sham operated rats at 5 days after operation. Whereas at 10, 20, and 30 days after nerve transection the response to SP was significantly increased as compared with sham operated rats. This phenomenon was also observed with neurokinin A (1.5, 3.0 and 6.0 nmol/rat), eledoisin (0.05 and 0.10 nmol/rat) and physalaemin (0.05 and 0.10 nmol/ rat) at 10 days after operation. Ipsilateral depletion of SP from the lumbar (L4-L6) spinal cord was observed at 5, 10, 20, and 30 days after the unilateral transection of the sciatic nerve. These results suggest that sciatic nerve transection may produce an increased response to tachykinins through an enhanced sensitivity of tachykinin receptors in the lumbar cord.

Notes: Summary Proteins of membranes and cytosols were extracted from the livers and brains of mice (inbred strain DBA/6J) and rats (inbred strain DA/Han) and separated by two-dimensional electrophoresis (2-DE). The 2-DE patterns were compared with regard to qualitative (spot position) and quantitative (spot intensity) characteristics of the proteins of these two species. The following results were obtained: (1) Brain had more (higher percentage) conservative proteins (proteins found in both mice and rats) than liver; (2) plasma membranes had more conservative proteins than the cytosols; (3) organ-unspecific proteins contained more conservative proteins than relatively organ-specific proteins; (4) the pattern of distribution of genetic variability among different classes of proteins represented by findings 1–3 was the same for the qualitative and quantative characteristics of the proteins; and (5) some observations indicated that quantitative variability occurred more frequently among proteins than did qualitative variability. Our conclusion is that regulatory sequences in the DNA (regulatory genes) are subjected to functional constraints that differ in strength among different classes of proteins by the same ratios as the constraints acting on the structural genes. The overall effect of the selective pressure is, however, less stringent for regulatory genes than for structural genes. The results obtained here by comparing two different species are very similar to previous results we obtained by studying different subspecies (inbred strains of the mouse). From this finding arises a new concept: the study of molecular evolution on the basis of different classes of proteins. Our results were compared with data from the literature that were obtained in part from studies on cultured cells. The comparison suggested that cultured cells have lost their tissue-specific proteins, and so generate predominantly extremely conservative proteins.

Notes: Summary The influence of the quality and the quantity of dietary proteins on the distribution of a single massive dose of vitamin A in various organs of growing Wistar strain rats has been studied by using casein and bengal gram diets at 20 % and 10 % protein levels. The distribution of [3H]-retinyl acetate in various tissues was also investigated in these dietary conditions. The results show that the hepatic storage of dietary as well as a single massive dose (20,000 I.U.) of vitamin A was profoundly decreased in the rats fed on bengal gram diets as compared to those fed on casein diets. Regardless of hepatic stores, the plasma vitamin A levels were comparable in all the groups. Feeding of low quality of protein reduced the tissue distribution of [3H]-retinyl acetate in control as well as rats given a massive dose of vitamin A. This study suggests that both the poor quality and the inadequate quantity of dietary protein are detrimental influences on the vitamin A status of the growing rats.

Notes: Summary Normal human breast organoids, derived by collagenase digestion of reduction mammaplasty tissue specimens, have been cultured in vitro for up to 28 days after injection into organ cultures of virgin rat mammary fat pads. The culture medium was serum-free Waymouth's MB 752/ 1 with hormonal additives. The rat mammary tissue responded well to growth-promoting and lactogenic stimuli in the culture medium, in agreement with previous investigations. Using immunohistochemistry casein was identified in rat epithelia exposed to lactogenic medium. Human organoids in culture remained viable but did not show hormone-responsiveness. Electron microscopy confirmed the presence of both luminal epithelial cells and myoepithelial cells. The serum-free culture of normal human breast organoids in a three-dimensional matrix provides a system in which to study factors controlling growth and differentiation.

Notes: Summary Cardiac output and its distribution were studied in rats made septic by an i.p. injection of liveE. coli bacteria and in controls given an equivalent amount of saline. The E. coli injection was followed by signs of severe shock in eight of 12 rats. Control animals all survived with only minor changes in cardiac output and peripheral hemodynamics. Blood flow in shocked animals was characterized by a reduction of cardiac output, while myocardial and cerebral flows were not reduced. The intact circulation to the brain and to the heart in the shocked rats was at the expense of kidney, spleen, and skin blood flows.

Notes: Summary Effects of degradable starch microspheres administered via the hepatic artery were examined in rats in which an adenocarcinoma was transplanted into the liver.3H-uridine or3H-uracil with cold uridine and uracil, respectively, in amounts corresponding to therapeutic doses of these two pyrimidines as fluoro compounds, were administered with or without microspheres. Labeling of the acid-soluble fraction and RNA of tumor, liver, small intestine, spleen, kidney, and bone marrow was examined after 3 and 60 min after injection. When microspheres were added, the specific radioactivity of tumor RNA was significantly higher at both 3 min (P 〈 0.05) and 60 min (P 〈 0.01) in the rats given uridine, and in rats given uracil it was higher at 60 min after injection (P 〈 0.05). There were no such differences in the labeling of the normal tissues. The results indicate that arterial administration of cytostatic drugs, such as 5-fluoropyrimidines, together with degradable starch microspheres might increase the cytotoxic effect on tumors nourished by the artery.

Notes: Summary The effects of dietary composition in combination with chronic ethanol ingestion on pancreatic proteolytic-antiproteolytic systems were studied by submitting 192 male Wistar rats to a 12-week dietary period. The rats were fed with a standard (S), fat-rich (F), protein-rich (P), or carbohydrate-rich (C) diet after randomized division into four groups. Half of the animals in each dietary group received water and the other half a mixture of 15% (v/v) ethanol and water as their drinking solution. The C-diet caused a significant increase of BAPNA hydrolysis, which was even more pronounced in rats receiving ethanol. Casein hydrolysis was increased significantly by the C-diet, but ethanol did not have any significant effect on this. Hydrolysis of ATEE was decreased significantly by the P- and C-diets, and ethanol in combination with the S- and F-diets decreased hydrolysis of ATEE in comparison with the corresponding water-receiving groups. The trypsin-inhibiting capacity of the pancreatic tissue was significantly increased in the group receiving C- and F-diets as compared to the S-diet-receiving group of animals. It seems that the composition of the consumed diet in combination with chronic ethanol ingestion may play a role in regulating the pancreatic proteolytic-antiproteolytic system. However, these changes were not parallel. The trypsin-inhibiting capacity of pancreatic tissue was also affected by the quality of the diet.

Notes: Summary Subtotal or total liver ischaemia was induced in the rat by dividing the hepatic artery (Expt. I) or by total dearterialisation of the liver (Expt. II) 2 days after porta-caval shunt (PCS). The animals received i.v. a 10% glucose infusion for 5 h after the last operation and were killed by decapitation. At the end of the experiment all animals with liver ischaemia were in Grade III coma. In different regions of the CNS 5-hydroxytryptophan (5-HTP), 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), were analysed by HPLC-technique with electrochemical detection, while dihydroxyphenylalanine (DOPA), dopamine (DA) and norepinephrine (NE) were analysed with a radio enzymatic method after blocking the decarboxylation of 5-HTP to 5-HT and DOPA to DA by inhibition of the aromatic amino acid decarboxylase enzyme with m-hydroxybenzylhydrazine (NSD 1015) in order to estimate the synthesis rate of 5-hydroxyindoles and catecholamines. In Expt. I concentrations of 5-HTP in animals with PCS were increased as compared to sham operation. In animals with liver ischaemia, 5-HTP concentrations were increased as compared to sham operation but similar to those in animals with PCS alone. These results suggest that ligation of the hepatic artery for 5 h in PCS animals does not further accelerate the rate of brain indole synthesis. In Expt. II, the 5-HTP concentrations were increased in PCS animals as compared to sham operation. Animals with total liver dearterialisation exhibited decreased 5-HTP levels as compared to PCS, suggesting a decreased brain indole synthesis after severe liver ischaemia. In Expt. II, CNS concentrations of DOPA following PCS were unaltered as compared with sham-operated animals. In animals with total liver dearterialisation, DOPA levels were increased, suggesting an augmented catecholamine synthesis. The NE levels were lower than in PCS and in shamoperated animals.

Notes: Summary The correlation between histological findings and mortality was studied in rat experimental acute pancreatitis (AP) modified by different diets and chronic ethanol consumption. Male Wistar rats (n = 192) were divided into eight groups and they were fed either a mixture of water and 15% (v/v) ethanol or tap water combined with standard or special diets for 12 weeks. The animals were followed up for 24 h after induction of AP, and the lowest mortalities were observed in the groups receiving water and standard (S) or carbohydrate-rich (C) diets and the highest in the groups receiving water and protein-(P) or fat-rich (F) diets. In the groups receiving S- or F-diets and ethanol the mortality was significantly increased. The animals were relaparotomized after 24 h of follow-up time. Histological specimens were taken from the surviving rats and evaluated on an arbitrary scale. Histologically, AP was the most severe in the group receiving the C-diet and ethanol, but in this group mortality did not differ significantly from the S-diet and water receiving group. The lack of correlation between the mortality and histological findings suggests nutritional factors to be important for the survival of the animals in experimental AP. It also stresses the assessment of the severity of experimental AP to be based on the all available parameters — not only on the basis of histological findings.

Notes: Summary Experimental testicular torsion must be used for certain studies of clinical relevance, but most experimental models either do not provide hemodynamic alteration comparable to the clinical situation or cannot guarantee reproducibility. Using a rat model arterial perfusion and hemorrhagic infarction were correlated to the degree of both intra- and extravaginal testicular torsion. Arterial inflow was measured sequentially with radiolabelled microspheres, hemorrhagic infarction was judged by the increase of testicular weight. Maximal hemorrhagic infarction and reproducible values were found when the spermatic cord was twisted togehter with the tunica vaginalis for 360°–540°.

Notes: Summary The effects of metoclopramide (MTC) and bromocriptine (BRC) (two drugs which act as antagonist and agonist of DOPA-receptors, respectively) on the zona glomerulosa of dexamethasone/ACTH-treated rats were investigated by coupled biochemical and morphometric techniques. Shortterm (1-h) MTC administration significantly increased the plasma concentration of aldosterone, while long-term (7-day) MTC administration, as well as short- and long-term treatment with BRC did not cause any apparent change. Long-term MTC administration was found to significantly potentiate both the rise in the plasma level of aldosterone and the hypertrophy of the zona glomerulosa and its parenchymal cells induced by a prolonged treatment with angiotensin II (AII), but not those evoked by a chronic sodium deprivation alone or combined with AII infusion. Long-term BRC administration notably counteracted the effects of sodium restriction (coupled or not with AII infusion), but not those induced by the administration of AII alone. Long-term MTC administration partially reversed both the lowering of the plasma concentration of aldosterone and the atrophy of the zona glomerulosa and its parenchymal cells caused by a prolonged sodium-loading (combined or not with captopril infusion), but not those produced by the administration of captopril alone. On the other hand, long-term BRC treatment induced a further significant reduction in the blood level of aldosterone and the volume of zona glomerulosa and its cells only in captopriltreated animals. These findings are consistent with the view that the dopaminergic system exerts a maximal tonic inhibitory effect not only on the secretory activity, but also on the growth and steroidogenic capacity of the rat zona glomerulosa. Furthermore, they suggest that the activity of the dopaminergic system is in turn controlled by the sodium balance, being almost completely suppressed by a prolonged sodium deprivation.

Notes: Summary In rats with a portacaval shunt (PCS), the effect on the serotonin metabolism in the brain after oral administration of blood, a mixed amino acid solution (Vamin 14; KabiVitrum, Sweden) or a 10% glucose solution was studied. One week after PCS, the animals were fed with a gastric tube for 8 h and thereafter tested for behavioral abnormalities before decapitation at 12 h. The concentration of 5-hydroxytryptophan (5-HTP), serotonin (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) were analyzed chromatographically (HPLC technique with electrochemical detection) in different regions of the brain. Estimation of synthetic rates of 5-hydroxyindoles was facilitated by aromatic aminoacid decarboxylase inhibition (m-hydroxybenzylhydrazine; NSD 1015). The brain concentrations of 5-HTP, 5-HT, and 5-HIAA were increased in all shunted rats as compared with sham-operated animals. Whether animals received blood, glucose, or aminoacid solution made no differences in the brain concentrations of 5-HTP and 5-HT. Concentrations of 5-HIAA were lower in those animals receiving blood as compared with the other shunted groups. No reproducible differences in the behavior of the animals were observed. These results suggest that massive blood administration 1 week after PCS in rats has no influence on the rate of brain indole synthesis. While alterations in serotonin metabolism may play a role in some forms of encephalopathy, this study implies that the behavioral and neurologic disorders which follow gastrointestinal tract hemorrhage in patients with liver failure may have other etiologies.

Notes: Summary The critical period of Purkinje cell degeneration and cerebellar hypoplasia due to bilirubin was examined in rats with transient hyperbilirubinemia induced by a serial subcutaneous injection of novobiocin from 1 to 3, 5 to 7, 10 to 13, or 16 to 20 days after birth. Animals showing total plasma bilirubin levels of 5 to 7 mg/100 ml 6 h after the final injection were used for this study. In nearly midsagittal sections of the culmen, the percentage of the affected Purkinje cells was 0.9%, 17.1%, 0% and 0% at days 3, 7, 13 and 20, respectively. Thus, the Purkinje cells were most vulnerable to bilirubin between days 5 and 7. Cerebella from the rats which showed transient hyperbilirubinemia at day 3, 7, 13 or 20 were weighed at day 30. The cerebellar weight was significantly low only in rats showing hyperbilirubinemia at day 7. Thus, the critical period of the cerebellar hypoplasia due to bilirubin coincided with the period when the Purkinje cells were most sensitive to bilirubin. These results suggest that the Purkinje cell damage leads to the cerebellar hypoplasia in hyperbilirubinemia.

Notes: Summary Glycogen accumulation in the Clarke's nucleus neuropil of young adult rats whose sciatic nerves were crushed in the first postnatal day was investigated with the electron microscope. Glycogen was observed in synaptic boutons and in small myelinated axons. In some terminals, glycogen accumulated in membranebound structures resembling mitochondria and formed large multigranular bodies which were entirely separated from the axoplasm. The multigranular body reached the size of 1.3 μm. Glycogen was present as single beta particles of about 25–40 nm in diameter and in aggregations of large alpha clusters. The astrocytic glycogen distribution was almost similar to that of the control specimens. Glycogen was not observed in other glial cells. It is probable that glycogen accumulation in synaptic terminals of partially deafferentiated Clarke's nucleus may result from impaired glycolysis due to deficient resupply of the distal axon with glycolytic enzymes caused by a defect in axoplasmic transport from the hypoplastic sensory neuronal perikarya.

Notes: Summary Bergmann glial (Golgi epithelial) cells in the cerebella of rats of various ages were stained by the rapid Golgi technique, and their radial stem processes were measured for length and diameter. Additionally, the average number of such processes per cell was counted, and the development of bushy lateral protrusions was quantified. The length of radial processes—depending on the thickness of the molecular layer—was found to increase up to the end of the 2nd year of life. This elongation was accompanied by a reduction of the mean process diameter which was, however, not sufficient to prevent an increase in the cytoplasmic volume of the elongating cells. A marked outgrowth of lateral protrusions was observed up to at least the 5th month of life. These data are compared with earlier findings on the development of rat brain stem fetal radial glia, and of rabbit retinal Müller cells. Common mechanisms of glial cell development are discussed.

Notes: Summary Maturation of the rat cochlea, from postnatal days 2 to 60, was studied using scanning electron microscopyt (SEM), with emphasis on stereocilia and tectorial membrane (TM). Two days after birth, the organ of Corti was very immature. An adult appearance of its surface was observed by day 16 in the basal turn, and by the end of the 3rd postnatal week in the apex. Stereocilia started their development first on inner hair cells. By contrast, the apical pole of outer hair cells ended its maturation before that of inner hair cells. Top-links were detected very early in inner hair cell stereociliary development (postnatal day 2). Marginal pillars temporarily attached the TM to the organ of Corti; they disappeared first in the apical region. This transient attachment seems to play a role in the coupling of outer hair cells to the TM, as prints of their longest stereocilia appeared at the undersurface of the TM by the same time. Moreover, these prints were more clear and regular at the base than at the apex of the cochlea. Results are discussed in relation to ultrastructural and functional data on rat cochlea maturation.

Notes: Summary Cholinergic traits in rat mandibular processes were examined histochemically, under the electron microscope, scope, at early developmental stages (Stages 20 to 23, by Christie's nomenclature). The histochemical reaction for detection of enzymes was performed by the thiocholine method. Nonspecific cholinesterase (EC 3.1.1.8) activity was found in ectomesenchymal cells, vascular endothelial cells, and in some epidermal cells at stages 20 and 21. The enzymatic activity was localized in the perinuclear and endoplasmic reticular cisternae. At stage 22, the number of cells with enzymatic activity decreased gradually, except in the case of the capillary endothelial cells. At stage 23, when the trigeminal nerve fiber was obvious in the mandibular processes, nonspecific cholinesterase activity was restricted to some of the endothelial cells and trigeminal ganglionic cells. In contrast, acetylcholinesterase activity was found on the membrane of trigeminal nerve fiber. Thus, the transient, nonspecific, cholinesterase activity, found in rat mandibular processes, may serve some functions in transmission, lipid metabolism or destruction of toxic cholinesters during the period that precedes organogenesis.

Notes: Summary The present light and electron microscopic study deals with the morphology and organization of Cajal-Smirnow ansiform fibers (AFs) in the molecular layer of the cerebellar cortex. The cerebella of normal adult rats were processed with Cajal's reduced silver method and conventional electron microscopy. With the silver method AFs appear as isolated elements or, more frequently, as small bundles of myelinated fibers, which emerge from the medullary rays, ascend through the granular, Purkinje cell and molecular layers and curve back to reenter the granular layer or cerebellar white matter. They traced an arciform trajectory of variable width and height in the molecular layer. Relatively large bundles of AFs were rarely found. The occurrence of AFs was confirmed in semithin sections as myelinated fibers of variable diameter ranging from 1 to 6 μm. Oligodendrocytes were often observed near AFs. At the ultrastructural level, the most common type of AF is large, with a relatively thin myelin sheath and a moderately dense axoplasm. Nodal or terminal synaptic differentiations were not observed. We suggest that AFs are misoriented cerebellar mossy fibers and their occurrence may be the consequence of a small-scale error in the axonal guidance of growing mossy fibers.

Notes: Summary Central distribution of efferent and afferent components of the pudendal nerve was examined in the rat by the horseradish peroxidase (HRP) method after HRP application to the central cut end of the pudendal nerve. The pudendal motoneurons were located in the dorsolateral, dorsomedial and lateral groups at L5 and L6. Each of the dorsolateral and dorsomedial groups constituted a slender longitudinal cell column. Pudendal motoneurons in the lateral group were scattered at L5, rostrodorsally to the dorsolateral group. The neurons in the dorsolateral and lateral groups were labelled with HRP applied to the nerve branch innervating the ischiocavernosus and sphincter urethrae muscles. The neurons in the dorsomedial group were labelled with HRP applied to the branch supplying the sphincter ani externus and bulbospongiosus muscles. Some dendrites of pudendal motoneurons in the dorsomedial group extended to the contralateral dorsomedial group. These crossing dendrites were observed not only in male rats but also in female. The average number of the pudendal motoneurons in the dorsolateral and dorsomedial groups were larger in male rats than in female. A few neurons of the intermediolateral nucleus at upper L6 were also labelled with HRP applied to the dorsalis penis (clitoridis) nerve. Axon terminals of the pudendal nerve were distributed, bilaterally with an ipsilateral predominance, to the gracile nucleus, as well as to the dorsal horn and dorsal commissural gray from L4 to S2. A few labelled axons were seen in the intermediolateral nucleus at L6 and S1. Axon terminals from the dorsalis penis nerve were distributed more medially in the dorsal horn than those from the perinealis nerve.

Notes: Summary Newborn rats were exposed to daily intraperitoneal injections of 10 mg lead nitrate per kg body weight for the first 15 postnatal days. The growth and mortality of the lead-exposed animals did not differ from their control litter-mates, injected with vehicle only. In our previous studies, focal hemorrhages and spongy areas as well as breakdown of blood-brain barrier to plasma proteins were shown by light microscopy in the cerebellar parenchyma of 15-day-old rats exposed to this dose. In spite of these signs of edema, measurements of brain tissue specific gravity did not show increased water content. In the present investigation we examined the ultrastructure of the brain lesions in these rats with low-dose lead encephalopathy, focusing on signs of edema, and evaluated astroglial reaction by immunocytochemical staining for glial fibrillary acidic protein (GFAP). The electron microscopic findings were compatible with extracellular edema in the cerebellum of 15-day-old lead exposed rats. The number of GFAP-positive cell bodies in the gray substance of the cerebellar cortex was increased in the 15-day-old lead-exposed rats as compared with the controls of the same age, a finding which is presumably related to the leakage of plasma proteins. Both these findings were lacking at 20 days of age, suggesting reversibility of the lead-induced changes.

Notes: Summary An antiserum against conjugated glycine was characterized and applied to cerebellar sections of rats and baboons that had been perfusion-fixed with glutaraldehyde. After immunosorbent purification the serum reacted with brain protein-glutaraldehyde-glycine conjugates, but did not stain similar test conjugates prepared from other amino acids, including GABA and β-alanine. In the rat cerebellum the glycine antiserum selectively labelled a subpopulation of Golgi neurons. Adjacent Vibratome sections treated with an antiserum against conjugated GABA revealed an about equally large subpopulation of immunopositive Golgi cells. A proportion of the Golgi cells that were cleaved by the plane of section contained both immunoreactivities. Additional evidence for a colocalization of glycine and GABA was obtained by postembedding staining of alternate semithin sections with the GABA antiserum and glycine antiserum, respectively. The ability of the antisera to distinguish between fixed glycine and GABA was corroborated by preincubation of the antisera with glutaraldehyde-amino acid fixation complexes: glycine complexes abolished staining with the glycine antiserum but had no effect on the GABA antiserum. The opposite effects were obtained with the GABA complexes. Matching the distributions of the respective immunoreactivities, [3H]glycine uptake was restricted to glomerulus-like structures in the granule cell layer whereas [3H]GABA uptake also occurred in punctate and fibrous profiles in the molecular layer. The baboon showed a distribution of glycine-like immunoreactivity similar to that in the rat, except that a few immunopositive neurons occurred in the molecular layer. The latter neurons were interpreted as outlying Golgi neurons; however, the possibility that they represent a subpopulation of basket cells could not be excluded. The Purkinje cells were negative in both species. Glial cells were weakly stained with the glycine antiserum but were strongly immunopositive after incubation with an antiserum raised against conjugates of the structurally similar amino acid β-alanine. The present data suggest that glycine and GABA occur in about equally large subpopulations of Golgi neurons. A subpopulation of the Golgi neurons appears to contain both glycine and GABA.

Notes: Summary Using anatomical criteria, the olivo-cochlear fibers ending in the organ of Corti (efferent fibers) have recently been separated into two systems: a lateral system innervating principally the inner hair cell (IHC) area and a medial system innervating mainly the outer hair cells (OHCs). Electrophysiological and biochemical experiments suggest that acetylcholine may be a neurotransmitter of these efferent fibers. However, efferent synapses that use acetylcholine as neurotransmitter have not yet been identified at the electron microscopic level. Using a pre-embedding immunoelectron microscopic technique with a monoclonal antibody against choline acetyltransferase (ChAT), we localized ChAT-immunostained fibers below both the IHCs and OHCs. In the inner spiral bundle, one type of ChAT-immunostained fibers was vesiculated and formed axo-dendritic synapses with the afferent auditory dendrites contacting the inner hair cells. A second type of ChAT-immunostained fibers seen in the inner spiral bundle was unvesiculated. Unstained vesiculated varicosities synapsing with the auditory dendrites were also seen in the inner spiral bundle. At the OHC level, ChAT immunostaining was found in nearly all the terminals synapsing with the OHCs. The finding of two types of ChAT-immunostained efferent synapses in the organ of Corti, i.e. axodendritic synapses in the inner spiral bundle and axosomatic synapses with the OHCs, supports the hypothesis that both the lateral and the medial olivocochlear systems use acetylcholine as a neurotransmitter. The finding of numerous unstained synapses in the inner spiral bundle, and some below OHCs, together with previous data about putative cochlear neurotransmitters, suggests the possibility of additional non-cholinergic olivo-cochlear systems. It might soon appear useful to reclassify efferents according to the nature of the different neurotrans-mitters/ co-transmitters found in the various efferent synapses of the organ of Corti.

Notes: Summary The development of spontaneous bioelectric activity (SBA) was studied in dissociated occipital cortex cultures prepared from 19 day old rat fetuses. All cultures, recorded one per diem from 5 to 33 days in vitro (div), showed SBA. Computer analysis of 76 extracellularly recorded single unit spike trains was carried out after selection on the basis of stationarity criteria. Statistically significant developmental trends were found in (i) interspike interval dependencies and (ii) fluctuations in mean firing rate, on the order of a minute or longer. The highly dependent firing patterns, including stereotyped bursting, were present mostly in the 9–12 div group, whereas minute-to-minute fluctuations in the intensity of firing were considerably more pronounced in the oldest group (22–33 div) than in the younger cultures. In addition, firing categories defined on the basis of factor-analysis revealed that such fluctuations were almost exclusively to be found in neurons which fired in a pronounced ‘burst’, rather than a relatively continuous fashion. Only a few mature appearing synaptic structures were observed electron microscopically prior to 12 div, but increased steadily in number thereafter. No cultures prior to 14 div, but all cultures older than this, stained positively for the presence of glutamic acid decarboxylase. An extensive immunoreactive, putative GABAergic, network was present by three weeks in vitro.

Notes: Summary High pressures of helium affect the physiology of the central nervous system in animals and humans. We examined these effects in rat hippocampal slices. The in vitro preparation displayed a reversible reduction in postsynaptic and antidromic field potentials of CA1 pyramidal cells, but no significant change in the amplitude of the afferent volley. Although the subliminal synaptic response of CA1 neurons was depressed, the ability of these cells to produce population spikes was enhanced. These changes resembled those previously found in vivo in the rat hippocampus. The present results support the hypothesis of a helium pressure-induced depolarization of hippocampal neurons. Other possible mechanisms are discussed.

Notes: Summary In behaving rats, unit activity in the mitral and granule cell layers of the olfactory bulb (OB) can be modulated by respiration. In order to determine whether central influences could take part in this phenomenon, respiratory rhythm and the activity of OB units were recorded in the present experiment and analyzed temporally in 18 anaesthetized tracheotomized rats. In spite of the interrupted nasal airflow, 30 of the 80 cells recorded in the mitral and granule cell layers, still displayed a significant respiratory patterning of their activity. Maximal neuronal discharges were time-locked with different phases of the respiratory cycle, most often synchronized with the end of expiration. This is in contrast with previous observations in intact animals. Possible underlying mechanisms are discussed.

Notes: Summary The fate of monoclonal anti-vasopressin antibodies (VP-MAbs) injected in vivo into the paraventricular nucleus (PVN) of the rat brain was studied by immunocytochemistry. Depending on the post survival time, VP-MAbs contained in an ascites fluid were stained at different levels of the VP neurons: the cytoplasm of the PVN neurons, the fibres of the median eminence and the granular layer of the Gyrus Dentatus. The identification of endogenous peptides synthesized by PVN neurons showed that the VP-MAbs uptake was specific: it did not appear either in the oxytocinergic neurons or in the non immunoreactive neurons of the Brattleboro rat brain, this rat being genetically incapable of synthesizing central VP. Conversely, VP-MAbs only penetrated into the VP neurons: ascites fluid containing monoclonal antibodies prepared against bovine thyroglobulin (the carrier conjugated to VP in our immunizations) was neither stained in magnocellular neurons nor carried in nerve fibres. The neuronal uptake and transport of VP-MAbs occurred in vivo: they were totally inhibited by heating of the ascites fluid at 56° C for 30 min; this treatment did not alter the VP-MAbs themselves but probably destroyed some thermic sensitive component essential to the macromolecule internalization. The biological effects of antibodies injected in vivo have been reported. The results described here suggest that some specific antibodies passively transferred into the brain could act directly on the peptide synthesis recognized by the antibodies.

Notes: Summary The quantitative effects of dark-rearing and light exposure on the ultrastructural characteristics of synapses and synaptic boutons in layer 4 of the rat visual cortex (area 17) have been investigated using stereological techniques. Two experimental groups (each containing 5 animals) were investigated i) animals dark-reared upto weaning at 21 days post natum (21DPN) and then light exposed until 52DPN (Group 21/31), and ii) littermate animals totally dark-reared until 52DPN (Group 52dD). The results indicate a significantly higher mean density of synapses in the neuropil of layer 4 in group 21/31 (3.58×108 · mm-3) compared with group 52dD (2.68×108 · mm-3). Although the density per unit volume of synapses with identified asymmetrical synaptic membrane specialisations was not significantly different in group 21/31 than in group 52dD (but was significantly lower than animals reared normally), the density of synapses with identified symmetrical synaptic membrane specialisations was about 200% higher in group 21/31 versus group 52dD. However, significant differences were detected in the number of asymmetrical synapses established by single synaptic boutons in group 21/31 (1.21 ± 0.11) compared with group 52dD (1.10 ± 0.09). On the basis of the numbers of post-synaptic targets contacted by an individual synaptic bouton, a significantly higher density of synaptic boutons was found in group 21/31 (2.32×108 · mm-3) compared with group 52dD (1.82×108 · mm-3). Furthermore, planar quantitative data indicated significant inter-group differences in the ultrastructure of asymmetrical and symmetrical synaptic boutons. The results of this study provide evidence indicating marked structural alterations in the synaptic connectivity of layer 4 of the rat visual cortex following the light exposure of rats dark-reared upto weaning. Indeed visual deprivation severely affected the ‘inhibitory’ circuitry in the major thalamorecipient territory of the visual cortex.

Notes: Summary Collateralization of cerebellar efferent projections to the oculomotor region, superior colliculus (SC), and medial pontine reticular formation (mPRF) was studied in rats using fluorescent tracer substances. In one group, True Blue (TB) was injected into the oculomotor complex (OMC), including certain paraoculomotor nuclei and supraoculomotor ventral periaqueductal gray (PAG), and Diamidino Yellow (DY) was injected into the medial pontine reticular formation (mPRF) or pontine raphe. The largest number of single-TB-labeled (paraoculomotor-projecting) cells was observed in the medial cerebellar nucleus (MCN) and posterior interposed nucleus (PIN), whereas the largest number of single-DY-labeled (mPRF-projecting) cells was in the MCN. Double-TB/DY-labeled cells were present in the caudal two-thirds of the MCN, suggesting that some MCN neurons send divergent axon collaterals to the paraoculomotor region and mPRF. In another group, TB was injected into the SC and DY into the mPRF. The largest number of single-TB-labeled (SC-projecting) cells was in the PIN, although a considerable number of cells was observed in the caudal MCN, and ventral lateral cerebellar nucleus (LCN). Single-DY-labeled (mPRF-projecting) neurons were primarily located in the central and ventral MCN, but were also present in the lateral anterior interposed (AIN) and in the LCN. Double-TB/DY-labeled neurons were observed in the caudal two-thirds of the MCN and in the central portion of the LCN. The most significant new findings of the study concerned the MCN, which not only contained neurons that projected independently to the paraoculomotor region, SC, and mPRF, but also contained a considerable number of cells which collateralized to project to more than one of these nuclei. The possibility that the MCN projects to the supraoculomotor ventral PAG (containing an oculomotor interneuron system) and to the mPRF, which in the cat and monkey contain neural elements essential to the production of saccadic eye movements, is discussed. The anatomical findings suggest that the MCN in the rat plays an important role in eye movement.

Notes: Summary Pituitary and gonadal disorders consistent with abnormal LHRH and LH secretion occur in streptozotocin-diabetic rats. A key role in the synthesis and regulation of LHRH and in the phasic LH release is played by the preoptic-suprachiasmatic region which is mainly formed by the medial preoptic area, the sexually dimorphic nucleus of the medial preoptic area, and the suprachiasmatic nucleus. Therefore we have studied this region by morphology and morphometry in normal and streptozotocindiabetic rats. In normal animals, the neurons of the above mentioned nuclei were morphologically and morphometrically dissimilar. Independent of their localization, reduced cytoplasmic and nuclear areas were observed in the neurons of diabetic animals. These lesions are consistent with hypotrophied neurons. Consequently, diabetes may impair both synthesis and regulation of LHRH and may therefore account for pituitary disorders, testicular atrophy, and lacking preovulatory LH peaks. The structural differences of the neurons of the three nuclei in normal animals underline their different physiological role. Yet, the similarity of the changes found in all three nuclei suggests a generalized hypofunction of the whole preoptic-suprachiasmatic region under diabetic condition.

Notes: Summary The inhibitory action of Purkinje cells on vestibulospinal tract (VST) cells was examined in rats deprived of climbing fibers with 3-acetylpyridine (3-AP) intoxication. In order to resolve discrepancies raised in previous studies with various means, special efforts were devoted to directly estimate Purkinje cell inhibition at synaptic levels by using intracellular recording, to avoid sampling bias by using a systematic survey of VST cells in each rat, and to evaluate the time-dependence of the effects of climbing fiber deafferentation by regular testing at 10 day intervals until 160 days after 3-AP intoxication. As compared with 661 VST cells impaled in 15 control rats, 1771 VST neurons impaled in 29 3-AP-treated rats revealed four basic changes in the monosynaptic inhibitory postsynaptic potentials (IPSPs) induced by stimulation of Purkinje cell axons in the white matter of the cerebellar anterior lobe. First, the rate of IPSP occurrence among VST cells was 0.64 in control rats; at more than 10 days after 3-AP intoxication it decreased gradually, down to 0.37–0.38 at the 70th–81st days, and thereafter increased up to 0.53 by the 160th day. The rate of IPSP occurrence varied considerably between the rostral and caudal regions, and also between the dorsal and ventral divisions of the VST cell population, but its reduction after 3-AP intoxication occurred approximately in parallel in all divisions. Second, IPSPs evoked with standard 500 μA pulse stimuli were smaller in size on and after day 10. The reduction of IPSP size was by as much as 53% of control values at the 70th–101st days in the dorsal division, but no significant change occurred in the ventral division of the VST cell population. Third, the latency of the IPSPs was prolonged by about 0.25 ms on and after day 10. Analysis of the relationship between the IPSP latency and the dorsoventral location of VST cells in the medulla suggests that the major cause for the prolongation of IPSP latency is an increased synaptic delay at Purkinje cell axon terminals. Fourth, the cerebellar stimulation threshold for evoking IPSPs was almost always below 100 μA in control rats, but values of 100–250 μA were common after the 40th day. Thus, climbing fiber deafferentation exerts long-term influences on excitability of Purkinje cell axons, and on the connectivity and synaptic transmission from Purkinje cell axons to VST cells.

Notes: Summary Previous experiments have proven brain tissue transplantation effective in reversing lesioninduced behavioral deficits in mature rats. This study reversed the usual experimental paradigm, so that fetal substantia nigra was transplanted into intact neonatal rats and allowed to mature in the host brain. Upon maturation substantia nigra lesions were made bilaterally to reveal the functional contribution of the transplanted tissue. In control animals these lesions depleted striatal dopamine, producing rigidity, poverty of movement and abnormal posture comparable to Parkinson's disease in the human; cessation of feeding and drinking led to progressive weight loss and death. In contrast, fetal substantia nigra transplanted into the neonatal rat became well-integrated in the host brain and was shown to protect the animal from this syndrome produced by subsequent substantia nigra lesions. We suggest that transplantation in these neonatal rats was performed during a crucial period of synaptogenesis, an environment particularly favorable to host-transplant interaction.

Notes: Summary Following microinjection of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) into the medial prefrontal cortex (defined as the neocortical area innervated by the thalamic mediodorsal nucleus) labelled cells were observed in the pyramidal layer of the CA1 field of Ammon's horn. Observations made using antidromic stimulation confirmed these results, and revealed the slow conduction velocity of the fibres of the hippocampal cells innervating the prefrontal cortex. Taken together, these data provide evidence for a direct projection of CA1 cells to the medial prefrontal cortex.

Notes: Summary The medulla oblongata and pons of colchicine treated rats were analyzed with a doublestaining technique using mouse monoclonal antibodies to somatostatin and rabbit polyclonal antibodies raised against methionine-enkephalin. Numerous cells reacted with both antisera but cells reacting with only one antiserum were also observed. Double-stained cells were most frequently encountered at all levels of the nucleus tractus solitarii, in a well defined group in the caudal medullary reticular formation, along the lateral ventral surface of the medulla oblongata, dorsolateral to the inferior olive and in the nucleus raphe magnus. These findings provide further examples of coexistence of two peptides and indicate the possibility that somatostatin-and enkephalin-like peptides are co-released.

Notes: Summary Specificity testing should be performed under conditions identical to or closely similar to those of the immunocytochemical procedure. This paper describes a new model system that meets this requirement for postembedding immunocytochemistry of amino acids at the light- and electron microscopic levels. Test conjugates, obtained by reacting different amino acids with brain macromolecules in the presence of glutaraldehyde, were freeze-dried and embedded in an epoxy resin (Durcupan) exactly as for brain tissue. One section from each of the embedded amino acid conjugates and from a brain protein-glutaraldehyde conjugate (without amino acid) were piled on top of each other and embedded anew. Transverse semithin (0.5 μm) and ultrathin sections were cut through the stack. These test sections, in which all the different conjugates were represented, were then processed in the same drops of sera as the tissue sections to permit identical conditions for testing and immunocytochemistry. After immunogold labelling for electron microscopy, a quantitative expression of crossreactivity was obtained by computer-assisted calculation of gold particle densities over the different conjugates. The antisera used in the present study (glutamate anti-serum 13, taurine antiserum 20, and GABA antiserum 26) showed highly selective labelling of the respective amino acid conjugates and produced distinct labelling patterns in simultaneously processed cerebellar sections.

Notes: Summary We found that large cells in the dorsal root and trigeminal ganglia contained glutamate-like immunoreactivity. Immunoreactive neurons were not detected in the superior cervical or pterygopalatine ganglia. These findings indicated that glutamate is a neurotransmitter or neuromodulator of large cells of sensory ganglia.

Notes: Summary Neuronal response thresholds and the encoding of mechanical stimulus intensity in the ventro-basal (VB) thalamus was analyzed in anaesthetized rats before and during the first two hours following induction of hyperalgesic inflammation. This inflammation was induced by the intra-plantar injection of carrageenin in the hindpaw contralateral to the recorded neurones. Only neurones exclusively driven by noxious stimuli and with a receptiv field on or including the injected paw were considered. In this early phase of the inflammatory process, there was no significant modification of the response threshold to the mechanical stimulus (indentation of about 300μm). This suggests the involvement of additional neuronal population(s) to account for the decrease in the vocalisation threshold to pressure observed in the freely moving animal at this time of the inflammation, A liner encoding of the indentation depth was observed before and after the carrageenin injection although the slope of the stimulus response-curve was steeper after the injection. The data emphasize that the carrageenin-sensitization acts differentially on the liminal and supra-liminal responses of the same neurone to a skin indentation, since in the first hour following the initiation of the inflammation the sensitization is essentially observed for responses obtained with stimulus intensity largely above the threshold value. With regard to previous observations using thermal stimulation, the results also illustrate that the carrageenin induced sensitization of responses differs depending on the stimulus intensity and modality used.

Notes: Summary Paired injections of fluorescent tracers (True Blue, Diamidino-Yellow) were made into the oculomotor complex (OMC) and medial pontine reticular formation (mPRF), and superior colliculus (SC) and mPRF, in adult rats to retrogradely label the cortical cells of origin of projections to these oculomotor-related brainstem structures. While large numbers of single-labeled cells in the medial frontal cortex projected only to the mPRF, the presence of many double-labeled cells in the dorsomedial shoulder cortex (medial precentral/anterior cingulate areas), the rat frontal eye field (FEF), indicated that this cortical region contains lamina V pyramid neurons whose axons collateralize to project to the region of the OMC, SC, and mPRF. The similarities of rat and monkey FEF connections, and their relevance to the control of eye movement, are discussed.

Notes: Summary The effects of low pass filtering on the brainstem auditory evoked potential (BAEP) were studied in the adult male rat. The bandpass of the recording system was progressively widened while the cut-off frequency of the high pass filter remained constant at 3.2 Hz. When the high frequency cut-off was 320 Hz or less, the principal waveform recorded in response to a click stimulus was a slow positive-negative complex. As the high frequency setting was raised from 800 Hz to 3.2 kHz, the slow components of the brainstem were replaced by four fast BAEP waves (I, II, III and IV). As the bandpass widened there was an increase in amplitude and a decrease in the absolute latency of all four fast waves in the order of 0.1 ms although the wave I–IV interpeak latency remained unaffected. The results confirm that the high frequency components of the BAEP are underlain by a slow positivity of uncertain origin followed by a slow negativity which probably arises within the inferior colliculus.

Notes: Summary The foreleg proprioceptive and cutaneous representations, in the Sm cortex of urethane-anesthetized rats was studied. Natural or electrical stimulations and stretches of single forearm muscles were used. Multiunitary, unitary or intra-cellular recordings were performed in the contra-lateral Sm cortex. The aims of the study were: 1 — to compare the proprioceptive and cutaneous maps 2 — to analyse the characteristics of the unitary responses and 3 — to study the laminar distribution of cutaneous and muscular inputs. It is shown that: 1 — the proprioceptive and cutaneous representations overlapped, except in the anterior part where only proprioceptive (mainly articular) responses were obtained. The representation of each stretched muscle extended over the whole cutaneous area, showing a total overlap between inputs from these muscles. 2–46% of the intracellularly recorded cells (n=215) responded to peripheral stimulation, and 30.7% were influenced by (at least) muscle stretch. The majority of excited cells showed cross-modal covergence, and among neurons responding to muscle stretch, 60% received inputs from the two muscles stretched. Two categories of EPSPs were found, and four neurons responded to cutaneous or muscular stimulation with a burst. 19% of the responding cells were inhibited by peripheral — mainly cutaneous — stimulations. 3 —Excited neurons were recorded in all layers, with just over half located in layer IV, whereas IPSPs were obtained mainly in layer V. The cells excited by cutaneous and muscular inputs (convergent neurons) were preponderant in layers IV to VI. This work shows that the cutaneous and muscular inputs reach the same area in Sm cortex, and that a majority of excited cells are “convergent”. The results are not in favor of an area 3a (by analogy with cats and monkeys) in the rat.

Notes: Summary The superior colliculus was removed from rats at either one or five days of age or in maturity. Four months later they were tested on two versions of a visual search task. Experiment 1 required animals to retrieve food pellets concealed in a depression in the top of identical narrow pillars arranged in an arena. Rats with lesions of the superior colliculus, regardless of the age at operation, showed a large number of ‘return’ errors compared with sham-operated controls. Return errors were defined as occasions on which the animal returned to pillars that had previously been visited on that trial, before every pillar had been visited at least once. Experiment 2 compared the ability of infantand adult-operated animals to detect and locate a single, baited white pillar in an array of black ones. There were no group differences in response latencies to targets presented in the rostral visual field (within 40° of the midline). However, animals operated on in adulthood or at 5 days of age were slower than both sham-operated animals and animals operated on at one day of age in their responses to more peripheral targets. The latter two groups were indistinguishable.

Notes: Summary Single unit activity was recorded from complex spike cells in the hippocampus of the rat while the animal was performing a spatial memory task. The task required the animal to choose the correct arm of a 4 arm plus-shaped maze in order to obtain reward. The location of the goal arm was varied from trial to trial and was identified by 6 controlled spatial cues which were distributed around the enclosure and which were rotated in step with the goal. On some trials these spatial cues were present throughout the trial (spatial reference memory trials) while on other trials they were present during the first part of the trial but were removed before the rat was allowed to choose the goal (spatial working memory trials). On these latter trials the animal had to remember the location of the cues and/or goal during the delay in order to choose correctly. 55 units were recorded during sufficient reference memory trials for the relationship between their firing pattern and different spatial aspects of the environment to be determined. 33 units had fields with significant relations to the controlled cues while 16 had significant relations to the static background cues, those cues in the environment which did not change position from trial to trial. Of 43 units which could be tested for their relation to the shape of the maze arms themselves, 15 showed such a relationship. Therefore the place units can be influenced by different aspects of the spatial environment but those related to the task requirement appear to be more potent. Interaction effects between the different spatial factors also influenced the firing pattern of some units. Of particular interest was the interaction between the controlled cues and the static background cues found in some cells since this might shed some light on how the hippocampus enables the rat to solve the memory task. 30 units with place fields related to the controlled cues were recorded during successful performance on spatial working memory trials as well as during spatial reference memory trials. The place fields of 90% of these units were maintained during the retention phase of the memory trials. During the recording of some units, other types of trial were given as well. On control trials, the cues were removed before the rat was placed on the maze. These trials provided controls for the potential influence of information left behind by the controlled cues and for the influence of the animal's behaviour on the unit activity. They also provided information about the unit firing in the absence of the controlled spatial cues and about the animal's choice of goal under these circumstances. During control trials, the units typically maintained their place fields but these fields had no relation to the experimenter-defined goal. The rat's choice of goal arm at the end of the trial, however, continued to show the usual spatial relationship to the fields. The data from these control trials, taken together with the interaction between the controlled cues and the static background cues seen in some of the cells and the characteristic mistakes made by each rat, suggest that the animal enters the task on each trial with an expected or preferred orientation of the controlled spatial cues relative to the background cues and that it must reorient its cognitive map of the environment or search for a different map when the actual orientation of the controlled cues departs from this default condition. Detour trials differed from working memory trials in that the animal was not immediately allowed to choose the goal at the end of the retention period but was forced to enter a non-goal arm instead. These trials ruled out the possibility that the animal was remembering the specific turn required to reach the goal and demonstrated that the place fields for the entire maze are set up as a result of exposure to the controlled spatial cues in any one of the start arms. Overall, the results provide strong support for the cognitive map theory of hippocampal function. In particular, they demonstrate that the representations of places within an environment are connected together to form a map, that the orientation of this map relative to an environment can be changed from trial to trial, and that this orientation is “remembered” following the removal of the controlled spatial cues.

Notes: Summary Receptive fields (RFs) of 36 taste (the 22 parabrachio-thalamic relay (P-T) and 14 non-P-T) and 23 mechanoreceptive neurons (7 P-T and 16 non P-T) were located in the oral cavity of rats. All of the taste and most of the mechanoreceptive units examined had an RF on the ipsilateral side of the tongue or palate, but some mechanoreceptive P-T and non-P-T units had RFs bilaterally. When the RFs of taste neurons were examined with the most effective of the four basic taste (the best stimulus) and non-best stimuli, no difference was noticed in the location of RFs between the P-T and non-P-T neurons. Though most of the P-T neurons (7/11) and all of the non-P-T neurons (6/6) had an RF for non-best stimuli at a region similar to that for the best stimulus, some P-T neurons (4/11) had an RFs for non-best stimulus outside the RF for the best stimulus and/or on the region separate from the RF for the best stimulus. The P-T neurons, responding vigorously to non-optimal stimuli as well as to the best stimulus, had an RF outside the RF for the best stimulus. RFs for mechanical stimulation were also examined in some taste and mechanoreceptive neurons. The mechanoreceptive P-T units rarely had an RF exclusively on the palate. Some mechanoreceptive units had an RF on the region where no taste RF has been found, e.g. the intermolar eminence and the folium of the hard palate.

Notes: Abstract The effect of increasing age on contractile performance and catecholamine receptor activity was investigated in a distal, predominantly fast twitch oxidative glycolytic (FOG) muscle from the plantar surface of the rat hindfoot. The ability of the flexor digitorum brevis (FDB), isolated from anesthetized rats and maintained in vitro, to undergo post-tetanic potentiation and a staircase response declined with age. Potentiation following repetitive stimulation was reduced by 50% in 2 year old rats and eliminated in 3 year old animals. The rate of muscle fatigue during intermittent tetanic stimulation also increased in aging muscles. FDB, regardless of age, did not develop a positive inotropic response to 10−6 M epinephrine applied in vitro, but 3 year old FDB generated a prolonged contracture. Contracture tension was approximately 25% of twitch tension and was maintained for 2–10 min in the continued presence of catecholamine. Contractures were eliminated by pretreatment with α-adrenergic antagonists or by removing Ca2+ from the bathing medium. In addition to decreased contractile capacity, aging muscles acquire a population of α-adrenergic receptors which may underlie some of the metabolic and structural changes associated with increasing age.

Notes: Abstract We studied the effects of inhibition of either prostaglandins or the role of prostanoids and the renin-angiotensin system on renal function in rats with congenital unilateral hydronephrosis. Wistar rats with congenital unilateral hydronephrosis were infused with normal saline (control), captopril dissolved in normal saline or indomethacin dissolved in a solution of sodium chloride and sodium carbonate. In the control group both glomerular filtration rate (GFR) and effective renal plasma flow were reduced in the right hydronephrotic kidney (RHK) compared with the normal left kidney. Indomethacin did not improve renal function in the RHK. Captopril significantly improved GFR in the RHK. These results support the conclusion that the renin-angiotensin system is an important mediator of reduced GFR in congenital unilateral hydronephrosis in rats.

Notes: Abstract The subtype of dopamine (DA) receptors mediating the yawning response to DA agonists was determined in rats. Yawning was elicited both by the mixed D1–D2 agonist apomorphine and by the specific D2 agonist LY 171555, but not by the selective D1 agonist SKF 38393. Both apomorphine- and LY 171555-induced yawning were antagonized not only by the selective D2 antagonist sulpiride but, unexpectedly, also by the selective D1 antagonist SCH 23390. The results suggest that DA receptors mediating the yawning response are of the D2 type, and that these receptors are connected with D1 receptors in such a way that the blockade of the latter results in the functional inactivation of the former.

Notes: Abstract Rats were trained to detect the stimulus properties of pentylenetetrazol (PTZ), 16 mg/kg, and prototypic drugs for mu, kappa and sigma opioid receptors were tested for their ability to block or substitute for PTZ. Only the sigma agonist, phencyclidine, showed any capacity for blocking the PTZ stimulus. Drugs with selective kappa or sigma actions did not substitute for PTZ. However, morphine, fentanyl and Mr 2034 did substitute for the PTZ stimulus. This substitution was found to be centrally mediated in that quaternary morphine did not produce a PTZ-like stimulus. In contrast to the substitution of these drugs for PTZ, in rats trained to detect the stimulus properties of fentanyl, no substitution of PTZ for the fentanyl stimulus occurred. In tests of the capacity of various drugs to block the PTZ-like stimulus of mu agonists, the stimulus produced by morphine or fentanyl was blocked by naloxone, diazepam and haloperidol, but not by scopolamine. These results demonstrate that drugs with mu agonist properties show a one-way substitution for the discriminative stimulus produced by PTZ. The observation that haloperidol blocked the PTZ-like stimulus of mu agonists suggests the possible involvement of dopaminergic mechanisms in the mediation of the effect.

Notes: Abstract Rats received subcutaneous injections of either nicotine (NIC; 0.05–0.8 mg/kg) or vehicle [VEH (phosphate buffer); 1 ml/kg] immediately after conditioning sessions in a place-conditioning paradigm (delay conditioning). NIC was paired for three delay-conditioning sessions with one environment of a three-compartment place-conditioning apparatus; VEH was paired with another environment. The subjects were then tested for place preference or aversion by determining the proportion of time spent in each compartment during a 15-min test session. Delay conditioning with NIC only produced a dose-related place aversion (greater time was spent in the VEH-paired chamber on test day). Place aversion was evident when NIC, 0.8 mg/kg, was administered either immediately or 5 min after conditioning sessions but not when given 15 min after conditioning. Chlorisondamine (5 μg, lateral ventricle), but not saline, administered 2 weeks prior to delay conditioning with 0.8 mg/kg NIC completely blocked the NIC-induced place aversion. These data suggest that delay conditioning with NIC produces place aversion by a central mechanism. Since standard conditioning (NIC injection immediately before the place-conditioning sessions) with NIC only produced dose-related place preferences (Fudala et al. 1985; Fudala and Iwamoto 1986), the time of administration of the unconditioned stimulus is a strong determinant of the place-conditioning effects of NIC.

Notes: Abstract Rats with a history of daily (21 days) amphetamine (2.5 mg/kg) treatment showed enhanced activity when under placebo in their amphetamine-associated environment. We found that this conditioned effect was reduced by haloperidol (0.06; 0.125; 0.25 mg/kg), pimozide (0.25; 0.5 mg/kg) and sulpiride (8; 16; 32 mg/kg) but only at doses similar to or, in the case of pimozide, higher than those required to antagonize the unconditioned stimulant effects of amphetamine (2.5 mg/kg). Conversely, we observed that clonidine (7; 15; 30; 60 μg/kg) or lithium regimen (between days 15 and 21) leading to lithium plasma levels of 1.3±0.1 mEq/1, abolished amphetamine-conditioned hyperactivity but did not affect the unconditioned stimulation of amphetamine or locomotor activity in control rats. Moreover, we found that hyperactivity induced by the daily anticipation of food delivery shared identical pharmacological sensitivity with the behavioural excitation produced by a conditioning history with amphetamine. In light of the antimanic properties of lithium and clonidine and the ability of this latter drug to reduce noradrenergic transmission, our findings raise the posibility that incentive activity may model noradrenergic-dependent aspects of mania.

Notes: Abstract Benzodiazepines, used in the clinic as anxiolytics, have in animal models been found specifically to attenuate behavioural suppression caused by response contigent aversive stimuli, non-reward or novelty. The effects have been interpreted in more general terms as “behavioural disinhibition” or “response perseveration” or in more specific terms as reduced “reward delay” or as an attenuation of a “behavioural inhibition system”. In a recent publication we have described an experimental test in which decision making in the rat can be studied. The model is derived from ethology, in particular from optimal foraging theory. In order to solve the task, the animal must choose correctly between two options. For each option the probability of its resulting in a reward (water) has to be estimated on the basis of available information and to be related to the cost of performing it. We found that diazepam, in a dose that did not significantly affect the ability to perform the options per se, caused a strong impairment when these options, on the basis of available information, had to be combined into functional sequences in a decision making procedure. The results obtained cannot be explained on the basis of disinhibition or response perseveration. The hypothesis is advanced that benzodiazepines alter decision making in a more nonspecific may, by, for example, affecting the evaluation of the learned significance of stimuli in the environment.

Notes: Abstract The actions of the serotonin precursor 5-hydroxytryptophan (5-HTP), the agonist 5-methoxy-N,N-dimetyltryptamine (MeODMT) and quipazine (QPZ) and the antagonists cyproheptadine, methysergide and metergoline, were studied in the rat and in the common marmoset (Callithrix jacchus). The precursor and agonists elicited head shakes, forepaw padding, splayed hindlimbs, tremor and Straub tail in the rat. However, head shakes were not observed after MeODMT and Straub tail was not observed after QPZ. Carbidopa plus 5-HTP potentiated only head shakes, while tranylcypromine (TCP) plus 5-HTP potentiated all the behaviors above. In the marmoset, the action of these drugs elicited drowsiness, teeth chattering, ataxia, vomiting and decreased motor activity, although vomiting was not elicited by MeODMT and ataxia and drowsiness by QPZ. Although TCP plus 5-HTP potentiated all these behaviors, carbidopa plus 5-HTP was not effective. Rats treated with the antagonists (1.0, 5.0 and 10 mg/kg doses) did not show any of these behaviors, but marmosets treated with the same drugs developed “drowsiness”, vomiting, and decreased motor activity; nonetheless, cyproheptadine (5.0 and 10 mg/kg doses) did not elicit “drowsiness”, while increasing motor activity and the number of head shakes. Pretreatment of marmosets with these antagonists blocked only teeth chattering elicited by MeODMT (4.0 mg/kg) and QPZ (10 mg/kg). Pretreatment with haloperidol, p-chlorophenylalanine and α-methyl-P-tyrosine had no effect. The data obtained show that rats and marmosets present differential behavioral responses to the 5-HT drugs used. Marmosets have a richer behavioral repertoire and show greater sensitivity to 5-HT agonists and antagonists. The data suggest that this animal might become a useful biological model for the study of central 5-HT systems.

Notes: Abstract Dexamphetamine (DEX) and chlordiazepoxide (CDZP) given together as mixtures have previously been shown to induce a characteristic “compulsive” form of locomotor hyperactivity in rats placed in unfamiliar environments, which was much greater than activity obtained with any dose of either drug given separately; acute pretreatment with lithium counteracted mixture-induced hyperactivity. The role of dopamine in these effects was investigated by measuring concurrently the levels of dopamine (DA), dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum. DEX (0.02-2 mg kg-1) increased horizontal (entries) and vertical (rears) activity, and increased DA and decreased DOPAC and HVA in the striatum. Chlordiazepoxide (CDZP) (12.5 or 20 mg kg-1) increased horizontal activity but did not affect vertical activity or DA or its metabolites. Lithium by itself in acute (2 meq kg-1, 24 and 4 h before test) or extended (2 meq kg-1 daily for 9 days) dosage had little effect on horizontal or vertical activity or levels of DA or DOPAC. Given together, DEX and CDZP (1.18 mg kg-1 + 12.5 mg kg-1), as expected, increased entries much more than did either drug given separately, but rears and levels of DA and metabolites remained similar to those with DEX given alone. Acute lithium pretreatment counteracted the mixture-induced increase in entries. Neither acute nor extended lithium pretreatment significantly altered DEX-induced changes in activity or levels of DA or DOPAC. The results suggest that an action on striatal DA neurones is responsible neither for the increases in entries seen after CDZP and CDZP/DEX mixtures (compared with DEX alone), nor for the attenuating effect of acute lithium on the mixture-induced increases. The changes in vertical activity (rearing) observed with DEX alone may, however, reflect an action on DA neurones. Animal models of “mania” are discussed.

Notes: Abstract The interaction between pimozide (a selective D2-dopamine receptor antagonist) and d-amphetamine on the operant performance of rats maintained under variable-interval schedules of positive reinforcement was examined. In Experiment 1, eight rats responded under variable-interval 30-s and variable-interval 300-s. Pimozide (0.0625, 0.125, 0.25, 0.5 mg/kg) suppressed performance maintained under both schedules in a dose-dependent manner, the degrees of suppression being equivalent in the two schedules. In Experiment 2, 12 rats responded under the same schedules. d-Amphetamine (0.1–3.2 mg/kg) suppressed performance under both schedules, the degree of suppression being somewhat greater in the case of variable-interval 30-s. Pre-treatment with pimozide (0.0625, 0.125 mg/kg) significantly attenuated the suppressant effect of d-amphetamine under both schedules. It is suggested that D2-dopamine receptors may be involved in mediating the suppressant effect of d-amphetamine on operant behaviour.

Notes: Abstract The behavioral effect of repeated methamphetamine (MAP) treatment was observed in young rat to establish the ontogenetic period crucial to methamphetamine sensitization. Animals were treated with MAP (2 mg/kg, SC) once daily for 5 days (Group 1: postnatal days 2–6, G-2: 7–11, G-3: 12–16, G-4: 17–21, G-5: 22–26, G-6: 27–31). Control animals were similarly treated with an equal volume of saline. On the 35th postnatal day, all rats were challenged with MAP (2 mg/kg, IP). Behavioral sensitization to MAP was not found in G-1, G-2, G-3 or G-4, although responsiveness to MAP was observed in rats after the 2nd postnatal day. The animals in G-5 and G-6 showed hypersensitivity to MAP in locomotor activity and stereotyped behavior. These findings indicate that the period crucial to behavioral sensitization to MAP corresponds to the period of presynaptic dopamine autoreceptor formation in the rat brain.

Notes: Abstract Latent inhibition (LI) is a behavioral paradigm in which prior exposure to a stimulus not followed by reinforcement retards subsequent conditioning to that stimulus when it is paired with reinforcement. Two experiments investigated the effects of 0.1 mg/kg haloperidol administration on LI as a function of number of CS pre-exposures. The investigation was carried out using a conditioned emotional response (CER) procedure consisting of three stages: pre-exposure, in which the to-be-conditioned stimulus, tone, was repeatedly presented without reinforcement; conditioning, in which the pre-exposed stimulus was paired with shock; and test, where LI was indexed by animals' suppression of licking during tone presentation. The three stages were conducted 24 h apart. In Experiment 1, 40 CS pre-exposures were given. LI was obtained in both the placebo and haloperidol conditions, but the effect was much more pronounced under the drug. Experiment 2 used ten CS pre-exposures. LI was not obtained in the placebo animals but was clearly evident in animals injected with haloperidol. The implications of these findings for the effects of neuroleptics on learning are discussed.