Distribution of antinociceptive adenosine A1 receptors in the spinal cord dorsal horn, and relationship to primary afferents and neuronal subpopulations

Adenosine can reduce pain and allodynia in animals and man, probably via spinal adenosine A1 receptors. In the present study, we investigate the distribution of the adenosine A1 receptor in the rat spinal cord dorsal horn using immunohistochemistry, in situ hybridization, radioligand binding, and confocal microscopy. In the lumbar cord dorsal horn, dense immunoreactivity was seen in the inner part of lamina II. This was unaltered by dorsal root section or thoracic cord hemisection. Confocal microscopy of the dorsal horn revealed close anatomical relationships but no or only minor overlap between A1 receptors and immunoreactivity for markers associated with primary afferent central endings: calcitonin gene-related peptide, or isolectin B4, or with neuronal subpopulations: mu-opioid receptor, neuronal nitric oxide synthase, met-enkephalin, parvalbumin, or protein kinase Cgamma, or with glial cells: glial fibrillary acidic protein. A few adenosine A1 receptor positive structures were double-labeled with alpha-amino-3-hydroxy-5-methyl-4-isoaxolepropionic acid glutamate receptor subunits 1 and 2/3. The results indicate that most of the adenosine A1 receptors in the dorsal horn are located in inner lamina II postsynaptic neuronal cell bodies and processes whose functional and neurochemical identity is so far unknown. Many adenosine A1 receptor positive structures are in close contact with isolectin B4 positive C-fiber primary afferents and/or postsynaptic structures containing components of importance for the modulation of nociceptive information.     

Preserved sigma1 (sigma1) receptor expression and behavioral efficacy in the aged C57BL/6 mouse

The sigma(1) (sigma(1)) receptor represents a unique intracellular neuronal protein modulating several neurotransmitter responses with relevant effects on cognitive functions. We examined here its expression and behavioral efficacy during aging. The sigma(1) receptor expression was examined in young (2 months old) and aged (24 months old) C57BL/6 mouse brain using comparative RT-PCR and immunohistochemistry. The promnesic effect of PRE-084, a selective sigma(1) agonist, was assessed using a water-maze procedure. The sigma(1) mRNA expression was not affected during aging in the olfactory bulb, hippocampus, hypothalamus, cortex or cerebellum. The sigma(1) immunolabeling was intense in the olfactory bulb, hippocampus, hypothalamus and midbrain of the young mouse and the distribution appeared unchanged in the aged. The subcellular localization was similar in aged and younger animals, the protein being present on nuclear, mitochondrial, endoplasmic reticular and plasmic membranes. At the behavioral level, aged C57BL/6 mice showed deficits in the invisible platform learning, but not when the platform was visible. Animals subjected to a transfer test under repeated treatment with saline or PRE-084 significantly learned the new platform location. This study shows that sigma(1) receptor expression is preserved in aged animals and demonstrates the efficacy of a selective sigma(1) agonist against age-related memory deficits. Targeting this unique receptor may offer an original drug strategy during aging.     

New data on the immunocytochemical localization of thyrotropin-releasing hormone in the rat central nervous system

An antiserum raised against the synthetic tripeptide pyroglutamyl-histidyl-proline (free acid) was used to localize thyrotropin-releasing hormone (TRH) in the rat central nervous system (CNS) by immunocytochemistry. The distribution of TRH-immunoreactive structures was similar to that reported earlier; i.e., most of the TRH-containing perikarya were located in the parvicellular part of the hypothalamic paraventricular nucleus, the suprachiasmatic portion of the preoptic nucleus, the dorsomedial nucleus, the lateral basal hypothalamus, and the raphe nuclei. Several new locations for TRH-immunoreactive neurons were also observed, including the glomerular layer of the olfactory bulb, the anterior olfactory nuclei, the diagonal band of Broca, the septal nuclei, the sexually dimorphic nucleus of the preoptic area, the reticular thalamic nucleus, the lateral reticular nucleus of the medulla oblongata, and the central gray matter of the mesencephalon. Immunoreactive fibers were seen in the median eminence, the organum vasculosum of the lamina terminalis, the lateral septal nucleus, the medial habenula, the dorsal and ventral parabrachial nuclei, the nucleus of the solitary tract, around the motor nuclei of the cranial nerves, the dorsal vagal complex, and in the reticular formation of the brainstem. In the spinal cord, no immunoreactive perikarya were observed. Immunoreactive processes were present in the lateral funiculus of the white matter and in laminae V-X in the gray matter. Dense terminal-like structures were seen around spinal motor neurons. The distribution of TRH-immunoreactive structures in the CNS suggests that TRH functions both as a neuroendocrine regulator in the hypothalamus and as a neurotransmitter or neuromodulator throughout the CNS.     

Cellular composition characterizing postnatal development and maturation of the mouse brain and spinal cord

The process of development, maturation, and regression in the central nervous system (CNS) are genetically programmed and influenced by environment. Hitherto, most research efforts have focused on either the early development of the CNS or the late changes associated with aging, whereas an important period corresponding to adolescence has been overlooked. In this study, we searched for age-dependent changes in the number of cells that compose the CNS (divided into isocortex, hippocampus, olfactory bulb, cerebellum, ‘rest of the brain’, and spinal cord) and the pituitary gland in 4–40-week-old C57BL6 mice, using the isotropic fractionator method in combination with neuronal nuclear protein as a marker for neuronal cells. We found that all CNS structures, except for the isocortex, increased in mass in the period of 4–15 weeks. Over the same period, the absolute number of neurons significantly increased in the olfactory bulb and cerebellum while non-neuronal cell numbers increased in the ‘rest of the brain’ and isocortex. Along with the gain in body length and weight, the pituitary gland also increased in mass and cell number, the latter correlating well with changes of the brain and spinal cord mass. The majority of the age-dependent alterations (e.g., somatic parameters, relative brain mass, number of pituitary cells, and cellular composition of the cerebellum, isocortex, rest of the brain, and spinal cord) occur rapidly between the 4th and 11th postnatal weeks. This period includes murine adolescence, underscoring the significance of this stage in the postnatal development of the mouse CNS.     

Reelin immunoreactivity in the adult sea lamprey brain

The expression of reelin, a large extracellular matrix glycoprotein, was studied in the brain of pre-spawning adult sea lampreys by immunohistochemistry using two monoclonal antibodies against this protein. Reelin immunoreactive (reln-ir) neurons were observed in the olfactory bulb, and pallial and subpallial regions in the telencephalon. In the diencephalon, reln-ir cells were observed in some hypothalamic nuclei, in the nucleus of Bellonci, and in the habenula. In the mesencephalon, this protein was detected in several nuclei related with the centrifugal visual system, although the optic tectum was devoid of immunoreactivity. The hindbrain showed several nuclei with immunopositive neurons, including the branchiomeric nerve motor nuclei and also some groups of non-giant cells of the reticular formation. The rostral spinal cord showed some immunopositive neurons mainly located in lateral and ventral positions. Overall, the pattern of distribution of reelin in the adult sea lamprey correlates with the previously reported in other adult vertebrates. Furthermore, the wide distribution of reelin in the adult lamprey brain is consistent with a possible existence of different roles for this protein not related with development in the central nervous system (CNS) of vertebrates (i.e. neuronal plasticity and/or maintenance).     

Expression of adenosine A2a receptors gene in the olfactory bulb and spinal cord of rat and mouse

The expression of adenosine A2a receptors (A2aR) in the mammalian striatum is well known. In contrast the exact distribution of A2aR in other regions of the central nervous system remains unclear. The aim of this study was to investigate the A2aR gene expression in the rat olfactory bulb and spinal cord, two regions which are seldom included in mapping studies. Secondly, we compared the A2aR expression in the rat and in the mouse brain. Hybridization histochemistry was performed with an S35-labelled radioactive oligonucleotide probe. The results show strong expression of A2aR in the mouse and rat striatum in accordance with previous reports. In the olfactory bulb a weak but specific expression of A2aR was found in the granular cell layer in both species. In contrast, no significant expression of the A2aR gene was observed in other parts of the brain or the rat spinal cord. The presence of the A2aR in the mammalian olfactory bulb suggests a functional role for this receptor in olfaction.     

微囊化异种嗅球组织移植联合药物干预修复受损脊髓的研究

目的:研究微囊化异种嗅球组织移植联合β-七叶皂甙钠对脊髓继发性损伤的治疗保护作用及机制。方法:健康SD大鼠180只,随机分为损伤对照组、微囊化兔嗅球组织移植组、微囊化兔嗅球组织移植联合β-七叶皂甙钠治疗组,损伤组又设1、3、7、14、28d5个时相点,紫外分光光度计检测脊髓伊文氏蓝含量;免疫组织化学观察血管内皮生长因子(VEGF)的表达;神经功能评分法(BBB法)评价大鼠术后运动功能的恢复情况。结果:脊髓损伤后脊髓伊文氏蓝含量增加、VEGF表达下调,大鼠的运动功能缺失,经微囊化异种嗅球组织移植联合β-七叶皂甙钠治疗后血脊髓屏障的通透性有所改善,VEGF表达上调,大鼠的运动功能有所恢复。结论:微囊化异种嗅球组织移植对脊髓继发性损伤有较好的疗效,联合应用嗅球组织细胞和β-七叶皂甙钠在脊髓损伤修复治疗中具有协同作用。     

Receptor for calcitonin gene-related peptide: localization in the dorsal and ventral spinal cord.

Although the distribution of calcitonin gene-related peptide has been extensively studied in the spinal cord, little is known about the precise subcellular localization of receptors for calcitonin gene-related peptide. The present study was undertaken to localize calcitonin gene-related peptide receptors in both the dorsal and ventral horns of the rat spinal cord. Immunocytochemical localization with specific monoclonal antibodies was performed at the light and electron microscopic levels. Calcitonin gene-related peptide receptor was expressed in neuronal but not glial elements. Discrete postsynaptic localization of receptor for the calcitonin gene-related peptide was evident in the cells and dendrites of the superficial dorsal horn. Some of the terminal endings apposing the stained synapses formed the central terminals of glomerular complexes. The endings were scallop shaped (Type I), typical of primary afferent terminations. Other dorsal horn structures with postsynaptic labeling were contacted by dome-shaped or elongated axonal endings. Presynaptic localization on some dorsal horn terminations may serve an autoreceptor function. Motoneurons, on the other hand, were contacted by axonal terminals with presynaptic calcitonin gene-related peptide receptors. These data suggest that (i) dorsal horn neurons are capable of direct primary afferent, calcitonin gene-related peptide receptor-mediated interactions and (ii) neuronal terminals contacting motor horn cells can be influenced through presynaptic paracrine-like calcitonin gene-related peptide receptor-mediated interactions. Thus, calcitonin gene-related peptide can have multiple modulatory effects on spinal cord neurons through site-specific receptors.     

Spinal cord transection modifies neuronal nitric oxide synthase expression in medullar reticular nuclei and in the spinal cord and increases parvalbumin immunopositivity in motoneurons below the site of injury in experimental rabbits

Using immunohistochemistry, we detected the expression of neuronal nitric oxide synthase (nNOS) in ventral medullary gigantocellular reticular nuclei and in the lumbosacral spinal cord 10 days after thoracic transection in experimental rabbits. We tried to determine whether neurons located below the site of injury are protected by the calcium binding protein parvalbumin (PV). Changes of nNOS immunoreactivity (IR) in spinal cord were correlated with the level of nNOS protein in dorsal and ventral horns. Ten days after transection, nNOS was upregulated predominantly in lateral gigantocellular nuclei. In the spinal cord, we revealed a significant increase of nNOS protein in the dorsal horn. This is consistent with a higher density of punctate and fiber-like immunostaining for nNOS in laminae III-IV and the up-regulation of nNOS-IR in neurons of the deep dorsal horn. After surgery, the perikarya of motoneurons remained nNOS immunonegative. Contrary to nNOS, the PV-IR was upregulated in α-motoneurons and small-sized neurons of the ventral horn. However, its expression was considerably reduced in neurons of the deep dorsal horn. The findings indicate that spinal transection affects nNOS and PV in different neuronal circuits.     

NADPH-diaphorase-positive neurons and pathways in the brain of the frog Rana esculenta

We described the NADPH-diaphorase-containing neurons and fibres in the brain of the frog Rana esculenta. In the telencephalon stained cells occurred in the olfactory bulb, all subdivisions of the pallium, the diagonal band, the medial septum and the striatum. The olfactory glomeruli showed the most intense enzyme reaction. The neuropil of the accessory olfactory bulb was also heavily stained and this staining extended to the rostral diencephalon through the ventral lateral pallium. Fibre staining was less intense in the medial pallium and the medial septum. In the diencephalon, NADPH-diaphorase staining was concentrated in the middle third of this part of the brain. The stained cells were embedded in a dense network of thin, stained fibres and terminals in the lateral anterior and central thalamic nuclei. Faintly stained cells were present also in the posterior preoptic nucleus, anterior thalamic nucleus, nucleus of Bellonci, corpus geniculatum thalamicum and the suprachismatic nucleus. In the mesencephalon, heavily stained cells occurred in the nucleus profundus mesencephali, anterodorsal, anteroventral and especially in the posterodorsal tegmental nuclei. Neuronal staining was less intense in the optic tectum and the torus semicircularis. Thick, intensely stained fibres occupied the lateral part of the tegmentum and the 7th layer of the tectum. A loose network of thin fibres occupied the periventricular area and all tegmental nuclei. In the rhombencephalon, the reticular nuclei and the inferior raphe nucleus showed the most intense staining, while some cells in the nucleus of the solitary tract and the dorsal column nuclei were less intensely stained. Heavy staining of fibres was characteristic of the spinal trigeminal tract, the solitary tract and the reticulospinal pathway.     

NADPH-diaphorase-positive neurons and pathways in the brain of the frog Rana esculenta

We described the NADPH-diaphorase-containing neurons and fibres in the brain of the frog Rana esculenta. In the telencephalon stained cells occurred in the olfactory bulb, all subdivisions of the pallium, the diagonal band, the medial septum and the striatum. The olfactory glomeruli showed the most intense enzyme reaction. The neuropil of the accessory olfactory bulb was also heavily stained and this staining extended to the rostral diencephalon through the ventral lateral pallium. Fibre staining was less intense in the medial pallium and the medial septum. In the diencephalon, NADPH-diaphorase staining was concentrated in the middle third of this part of the brain. The stained cells were embedded in a dense network of thin, stained fibres and terminals in the lateral anterior and central thalamic nuclei. Faintly stained cells were present also in the posterior preoptic nucleus, anterior thalamic nucleus, nucleus of Bellonci, corpus geniculatum thalamicum and the suprachismatic nucleus. In the mesencephalon, heavily stained cells occurred in the nucleus profundus mesencephali, anterodorsal, anteroventral and especially in the posterodorsal tegmental nuclei. Neuronal staining was less intense in the optic tectum and the torus semicircularis. Thick, intensely stained fibres occupied the lateral part of the tegmentum and the 7th layer of the tectum. A loose network of thin fibres occupied the periventricular area and all tegmental nuclei. In the rhombencephalon, the reticular nuclei and the inferior raphe nucleus showed the most intense staining, while some cells in the nucleus of the solitary tract and the dorsal column nuclei were less intensely stained. Heavy staining of fibres was characteristic of the spinal trigeminal tract, the solitary tract and the reticulospinal pathway.     

Distribution of neuropeptide Y-like immunoreactivity in the rat central nervous system--II. Immunohistochemical analysis

The distribution of neuropeptide Y-like immunoreactivity in the rat brain and spinal cord was investigated by means of the peroxidase-antiperoxidase procedure of Sternberger using a rabbit anti-neuropeptide Y serum. A widespread distribution of immunostained cells and fibres was detected with moderate to large numbers of cells in the following regions: olfactory bulb, anterior olfactory nucleus, olfactory tubercle, striatum, nucleus accumbens, all parts of the neocortex and the corpus callosum, septum including the anterior hippocampal rudiment, ventral pallidum, horizontal limb of the diagonal band, amygdaloid complex. Ammon's horn, dentate gyrus, subiculum, pre- and parasubiculum, lateral thalamic nucleus (intergeniculate leaflet), bed nucleus of the stria terminalis, medial preoptic area, lateral hypothalamus, mediobasal hypothalamus, supramammillary nucleus, pericentral and external nuclei of the inferior colliculus, interpeduncular nucleus, periaqueductal central gray, locus coeruleus, dorsal tegmental nucleus of Gudden, lateral superior olive, lateral reticular nucleus, medial longitudinal fasciculus, prepositus hypoglossal nucleus, nucleus of the solitary tract and spinal nucleus of the trigeminal nerve. In the spinal cord cells were found in the substantia gelatinosa at all levels, the dorsolateral funiculus and dorsal gray commissure in lumbosacral cord. The pattern of staining was found to be similar to that observed with antisera to avian and bovine pancreatic polypeptide, but to differ in some respects from that observed with antisera to molluscan cardioexcitatory peptide. The presence of neuropeptide Y immunoreactive fibres in tracts such as the corpus callosum, anterior commissure, lateral olfactory tract, fimbria, medial corticohypothalamic tract, medial forebrain bundle, stria terminalis, dorsal periventricular bundle and other periventricular areas, indicated that in addition to the localisation of neuropeptide Y-like peptide(s) in interneurons in the forebrain, neuropeptide Y may be found in long neuronal pathways throughout the brain.     

Mapping of the distribution of polysialylated neural cell adhesion molecule throughout the central nervous system of the adult rat: an immunohistochemical study.

In the nervous system, the neural cell adhesion molecule changes at the cell surface during development, from a form highly enriched in polysialic residues to several isoforms containing much less sialic acid, and is thought to participate in the structuring of neuronal groups and in the establishment of neuronal connections. Recent observations have indicated, however, that it may not be restricted to developing tissues since it is still present in certain adult neuronal centres which can undergo morphological reorganization. In this study, therefore, we examined systematically the distribution of polysialylated neural cell adhesion molecule immunoreactivity throughout the central nervous system of adult male and female rats, using light microscopic immunocytochemistry and immunoblot analysis with an antibody that specifically recognizes the polysialic residues of the molecule. Concomitantly, we compared this immunoreactivity to that due to all isoforms of the neural cell adhesion molecule, detected with a polyclonal serum raised against the NH2-terminal of the protein. Immunoreactivity due to the polysialylated isoform was consistently visualized in several discrete areas of the adult brain and spinal cord. An intercellular punctate immunolabelling characterized the staining in certain hypothalamic and thalamic nuclei, superficial laminae of the dorsal horn of the spinal cord, ventral portion of the dentate gyrus of the hippocampus, lateral geniculate, parabrachial and habenular nuclei, bed nucleus of the stria terminalis, mesencephalic central gray and olfactory bulb. In other areas, such as the piriform cortex, dorsal aspect of the dentate gyrus and fimbria and lamina X of the spinal cord, isolated neuronal-like cells were either completely filled with immunolabel or showed a surface reaction on their cell bodies and processes. Highly immunoreactive isolated glial-like cells were also noted within the ependymal layer of the central canal and lateral ventricles and at times in the peripheral white matter of the spinal cord. In contrast to this discrete localization, staining due to all isoforms of the neural cell adhesion molecule was widespread and diffuse throughout the brain and spinal cord. The expression of the polysialylated isoform in the supraoptic nucleus and hippocampus was confirmed by immunoblot analysis; it occurred together with weakly sialylated isoforms. No obvious differences were detected in the amount or distribution of immunoreactivity due to the polysialylated isoform in relation to the sex or age of the animals (between three and 12 months of age). Our study thus demonstrates that well-defined areas of the central nervous system of the adult rat continue to express the polysialylated isoform of the neural cell adhesion molecule.(ABSTRACT TRUNCATED AT 400 WORDS)     

Distribution of gephyrin in the human brain: an immunohistochemical analysis

Gephyrin is an ubiquitously expressed protein that, in the central nervous system, generates a protein scaffold to anchor inhibitory neurotransmitter receptors in the postsynaptic membrane. It was first identified as a protein component of the glycine receptor complex. Recent studies have demonstrated that gephyrin is colocalized with several subtypes of GABA(A) receptors and is part of postsynaptic GABA(A) receptor clusters. Here, we describe a study of the regional and cellular distribution of gephyrin in the human brain, determined by immunohistochemical localisation at the light and confocal laser scanning microscopic levels. At the regional level, gephyrin immunoreactivity was observed in most of the major brain regions examined. The most intense staining was in the cerebral cortex, hippocampus and caudate-putamen, in various brainstem nuclei with more moderate levels in the thalamus and cerebellum. At the cellular level gephyrin immunoreactivity was present on the plasma membranes of the soma and dendrites of pyramidal neurons throughout the various cortical regions examined. In the hippocampus, intense staining was observed on the granule cells of the dentate gyrus, and neurons of the CA1 and CA3 regions showed intense punctate gephyrin staining on their apical dendrites and cell bodies. Gephyrin immunoreactivity was also observed on neurons in the thalamus, globus pallidus and substantia nigra. In the putamen intense labelling of the striosomes was observed; most of the medium-sized neurons in the caudate-putamen were weakly labelled and many large neurons of the striatum were conspicuously stained. Many of the brainstem nuclei, notably the dorsal motor nucleus of the vagus, hypoglossal nucleus, trigeminal nucleus and inferior olive were all labelled with gephyrin. The spinal cord also showed high levels of gephyrin immunoreactivity. Our results demonstrate that the anchoring protein gephyrin is ubiquitously present in the human brain. We therefore suggest that gephyrin may have a central organizer role in assembling and stabilizing inhibitory postsynaptic membranes in human brain and is similar in function to those observed in the rodent brain. These findings contribute towards elucidating the role of gephyrin in the human brain.     

Neurokinin-1 Receptor Immunoreactive Neuronal Elements in the Superficial Dorsal Horn of the Chicken Spinal Cord: With Special Reference to Their Relationship with the Tachykinin-containing Central Axon Terminals in Synaptic Glomeruli

Synaptic glomeruli that involve tachykinin-containing primary afferent central terminals are numerous in lamina II of the chicken spinal cord. Therefore, a certain amount of noxious information is likely to be modulated in these structures in chickens. In this study, we used immunohistochemistry with confocal and electron microscopy to investigate whether neurokinin-1 receptor (NK-1R)-expressing neuronal elements are in contact with the central primary afferent terminals in synaptic glomeruli of the chicken spinal cord. We also investigated which neuronal elements (axon terminals, dendrites, cell bodies) and which neurons in the spinal cord possess NK-1R, and are possibly influenced by tachykinin in the glomeruli. By confocal microscopy, NK-1R immunoreactivities were seen in a variety of neuronal cell bodies, their dendrites and smaller fibers of unknown origin. Some of the NK-1R immunoreactive profiles also expressed GABA immunoreactivities. A close association was observed between the NK-1R-immunoreactive neurons and tachykinin-immunoreactive axonal varicosities. By electron microscopy, NK-1R immunoreactivity was seen in cell bodies, conventional dendrites and vesicle-containing dendrites in laminae I and II. Among these elements, dendrites and vesicle-containing dendrites made contact with tachykinin-containing central terminals in the synaptic glomeruli. These results indicate that tachykinin-containing central terminals in the chicken spinal cord can modulate second-order neuronal elements in the synaptic glomeruli.     

Thyrotropin releasing hormone (TRH)-immunoreactive cell groups in the rat central nervous system

Summary Using a paraformaldehyde-picric acidglutaraldehyde-containing fixative and treatment of the tissue with sodium borohydride, numerous and widespread TRH-immunoreactive cell bodies were observed in the central nervous system of colchicinetreated rats, including the olfactory bulb, cortical and hippocampal areas, the caudate nucleus and other subcortical areas, many hypothalamic nuclei, the periaqueductal central gray, pontine nuclei, medulla oblongata and the dorsal horn of the spinal cord. Most of these cells could not be visualized with the same antiserum when conventional fixation methods based on formalin alone were used. The present findings suggest that TRH systems are considerably more extensive than hitherto assumed.     

Distribution of 1,25-dihydroxyvitamin D3 receptor immunoreactivity in the rat brain and spinal cord

A complete mapping study on the 1,25-dihydroxyvitamin D3 receptor immunoreactivity within the rat central nervous system was performed with a monoclonal and a polyclonal antibody. Specific immunostaining was observed within both nuclear and cytoplasmic compartments of a variety of cells in the cerebellum, mesopontine area, diencephalon, cortex, spinal cord, and limbic system. Both monoclonal and polyclonal antibodies provided similar staining patterns. The monoclonal antibody stained distinct domains within the nuclei of all and the cytoplasm of specific neuronal cell types, like motor neurons, Purkinje cells, and pyramidal cells of the cortex more clearly than the polyclonal antibody. The expression of vitamin D3 receptor in the rat central nervous system was confirmed by in situ hybridisation. The widespread distribution of vitamin D3 receptor in distinct portions of the sensory, motor, and limbic brain systems suggests multiple functional properties of 1,25-dihydroxyvitamin D3 in the central nervous system.     

Pharmacological analysis of slow potentials recorded in frog olfactory bulb during natural stimulation

Pharmacological agents (strychnine, picrotoxin, pentobarbital, chloralose, GABA, penicillin, morphine) were used to investigate the nature of the slow potential recorded in the frog olfactory bulb in response to natural stimulation. Three possible hypotheses were tested: 1) The slow potential is neuroglial in nature; 2) it is the analog of the dorsal-root potential of the spinal cord and reflects depolarization of primary afferents arising in the terminals of the olfactory nerve and responsible for presynaptic inhibition in the frog olfactory bulb; 3) the slow potential reflects postsynaptic processes. The results showed great similarity between changes in the slow and dorsal-root potentials of the spinal cord in response to the action of pharmacological agents. However, the slow potential is evidently a complex response and incorporates at least one other component — depolarization of the dendrites of unknown nature.Translated from Neirofiziologiya, Vol. 7, No. 4, pp. 372–379, July–August, 1975.     

Afferent and efferent connections of the cortical and medial nuclei of the amygdala in sheep

The cortical (CoA) and the medial (MeA) nuclei of the amygdala are involved in the processing of olfactory information relevant to social recognition in the ewe. To better understand the neural pathways responsible for these effects, the connections of both CoA and MeA with the telencephalic and diencephalic regions were studied by injecting an anterograde (Biotin-Dextran-Amine, BDA) or a retrograde (Fluorogold, FG) neuronal tracer into either the CoA or the MeA. Concerning the primary olfactory structures, the CoA receives inputs from both the main olfactory bulb and the accessory olfactory bulb (AOB), while the MeA is innervated by cells only from the AOB. Among the other olfactory structures, only the entorhinal cortex and the tenia tecta are connected with both the CoA and the MeA. With respect to the other secondary olfactory structures, the connections with the CoA and the MeA show segregating neuronal routes. The CoA is connected with the accessory olfactory nucleus, the piriform, the endopiriform and the orbitofrontal cortices while the MeA exhibited connections with the nucleus of the lateral olfactory tract, the perirhinal and the insular cortices. Concerning the diencephalic structures, only the MeA receives projections from the PVN and the MBH. On the other hand, we showed that the BNST is the major site of connection with both the CoA and the MeA. Reciprocal projections were observed between the CoA and the MeA and between both nuclei and the basal or the lateral nuclei of the amygdala with the exception of the CoA which does not send inputs to the lateral nucleus. These data are discussed in relation with olfactory learning in the context of sexual and maternal behavior in sheep.