Distribution of nerve growth factor receptor-like immunoreactivity in the adult rat central nervous system. Effect of colchicine and correlation with the cholinergic system--II. Brainstem, cerebellum and spinal cord

Multiple nuclei and fiber tracts in the adult rat brainstem and spinal cord were found to contain nerve growth factor receptor-related protein, as recognized by the monoclonal antibody 192-IgG. Both cholinergic and non-cholinergic sensory and motor regions demonstrated immunoreactive cell bodies and fibers. Nerve growth factor receptor-immunoreactive cells were seen in the mesencephalic nucleus of trigeminal nerve, superior colliculus, parabrachial, prepositus hypoglossal, raphe, dorsal and ventral cochlear, interstitial nucleus of the vestibular nerve, ambiguus and reticular nuclei, cerebellum and ventral spinal cord. Immunoreactive cells resembling neuroglia were distributed subpially along the superior colliculus. Intracerebroventricular injection of colchicine resulted in significantly increased nerve growth factor receptor immunoreactivity in all previously positive neurons and especially in certain neurons of the cochlear and ambiguus nuclei. It also resulted in the visualization of receptor immunoreactivity in certain neurons which were normally non-immunoreactive including cerebellar Purkinje cells, neurons of the central gray, locus coeruleus, facial, dorsal motor vagal and hypoglossal nuclei. In normal animals, nerve growth factor receptor-immunoreactive fibers and varicosities occurred in the trigeminal nerve nuclei, pontine, vestibular, parabrachial, facial, hypoglossal, dorsal motor vagal, solitary, gracile and cuneate nuclei and spinal cord. Although most fiber-like immunoreactive structures were probably axons and nerve terminals, neuroglial or extracellular localizations could not be excluded in some areas. For example, the medial nucleus of the inferior olive and most cerebellar nuclei contained diffuse non-fibrillar receptor immunoreactivity. The presence of nerve growth factor receptor-like immunoreactivity in cell bodies and fibers of several sensory and motor areas of the adult rat brainstem, cerebellum and spinal cord suggests multifocal actions of nerve growth factor or a nerve growth factor-like substance. Although the degree of overlap between nerve growth factor receptor- and choline acetyltransferase-containing regions in the brainstem is not as great as in the forebrain, our findings suggest a potential influence of nerve growth factor or nerve growth factor-like substances on cholinergic systems outside the forebrain. Furthermore, the disparities which occur imply that non-cholinergic nerve growth factor receptor-containing neurons of the brainstem, cerebellum and spinal cord may be affected by such trophic substances.     

Neuropeptide Y in the olfactory system, forebrain and pituitary of the teleost, Clarias batrachus

Distribution of neuropeptide Y (NPY)-like immunoreactivity in the forebrain of catfish Clarias batrachus was examined with immunocytochemistry. Conspicuous immunoreactivity was seen in the olfactory receptor neurons (ORNs), their projections in the olfactory nerve, fascicles of the olfactory nerve layer in the periphery of bulb and in the medial olfactory tracts as they extend to the telencephalic lobes. Ablation of the olfactory organ resulted in loss of immunoreactivity in the olfactory nerve layer of the bulb and also in the fascicles of the medial olfactory tracts. This evidence suggests that NPY may serve as a neurotransmitter in the ORNs and convey chemosensory information to the olfactory bulb, and also to the telencephalon over the extrabulbar projections. In addition, network of beaded immunoreactive fibers was noticed throughout the olfactory bulb, which did not respond to ablation experiment. These fibers may represent centrifugal innervation of the bulb. Strong immunoreactivity was encountered in some ganglion cells of nervus terminalis. Immunoreactive fibers and terminal fields were widely distributed in the telencephalon. Several neurons of nucleus entopeduncularis were moderately immunoreactive; and a small population of neurons in nucleus preopticus periventricularis was also labeled. Immunoreactive terminal fields were particularly conspicuous in the preoptic, the tuberal areas, and the periventricular zone around the third ventricle and inferior lobes. NPY immunoreactive cells and fibers were detected in all the lobes of the pituitary gland. Present results describing the localization of NPY in the forebrain of C. batrachus are in concurrence with the pattern of the immunoreactivity encountered in other teleosts. However, NPY in olfactory system of C. batrachus is a novel feature that suggests a role for the peptide in processing of chemosensory information.     

Relaxin-3 in GABA projection neurons of nucleus incertus suggests widespread influence on forebrain circuits via G-protein-coupled receptor-135 in the rat

Relaxin-3 (RLX3) is a newly identified member of the relaxin/insulin peptide family that is highly conserved across a range of species from fish to mammals and is highly expressed in rat, mouse and human brain. Extensive pharmacological studies have demonstrated that RLX3 is a high affinity, selective ligand for G-protein-coupled receptor-135 (GPCR135, now classified as relaxin family peptide-3 receptor; RXFP3). In ongoing studies to understand the physiological functions of RLX3, the distribution of RLX3-containing neuronal elements in rat brain was determined by immunohistochemistry, using an affinity-purified polyclonal antiserum raised against a conserved segment of the RLX3 C-peptide (AS-R3(85-101)). Consistent with the distribution of RLX3 mRNA, neurons containing RLX3-like immunoreactivity (LI) were observed in the pontine nucleus incertus and the majority of these cells, which are known to express corticotropin-releasing factor receptor-1, were shown to express glutamic acid decarboxylase-65-immunoreactivity, suggesting a GABA phenotype. Nerve fibers and terminals containing RLX3-LI were observed adjacent to cells in the nucleus incertus and in various forebrain regions known to receive afferents from the nucleus incertus, including cortex, septum, hippocampus, thalamus, hypothalamus and midbrain. Regions that contained highest densities of RLX3-positive fibers included the medial septum, lateral preoptic area, lateral hypothalamus/medial forebrain bundle and ventral hippocampus; and additional fibers were observed in olfactory bulb and olfactory and frontal/cingulate cortices, bed nucleus of the stria terminalis, dorsal endopiriform, intergeniculate, and supramammillary nuclei, and the periaqueductal gray and dorsal raphe. The RLX3-positive network overlapped the regional distribution of GPCR135 mRNA and specific binding sites for an [125I]-GPCR135-selective, chimeric peptide. These anatomical findings further support the proposition that RLX3 is the endogenous ligand for GPCR135 in rat brain and provide evidence for broad modulatory activity of RLX3 in behavioral activation relating to autonomic and neuroendocrine control of metabolism and reproduction and higher-order processes such as stress and cognition.     

FMRFamide-like immunoreactivity in the brain and pituitary of the goldfish, Carassius auratus.

The distribution of FMRFamide-like immunoreactivity was determined in the brain and the pituitary of the goldfish, Carassius auratus. Immunoreactive perikarya were observed in the olfactory nerve, nucleus entopeduncularis, nucleus anterioris periventricularis, nucleus posterioris periventricularis, lateral part of the nucleus lateralis tuberis pars posterioris, midbrain tegmentum, and medulla oblongata. Immunoreactive fibers were widely distributed in the brain, in particular in the ventral telencephalon and the hypothalamus. A few immunoreactive nerve fibers were observed in the pituitary. The findings are discussed in relation to male sexual behavior and the involvement of FMRFamide-like peptide in pituitary functions in the goldfish.     

Orexin-A immunoreactive cells and fibers in the central nervous system of the axolotl brain and their association with tyrosine hydroxylase and serotonin immunoreactive somata

Orexin-A-like immunoreactivity in the axolotl brain was investigated by immunohistochemistry. Immunoreactive somata formed a single group in the hypothalamus, but were distributed beyond several nuclei, namely, the ventral aspect of the nucleus preopticus posterior, dorsal aspect of the nucleus suprachiasmaticus and anterior aspect of the pars ventralis hypothalami. Immunoreactive fibers were distributed throughout the brain from the olfactory bulb to the spinal cord except the cerebellum. The densest immunoreactive fibers were seen in the medial forebrain bundle and caudal lateral forebrain bundle. The largest number of immunoreactive puncta were seen in the mesencephalic tectum in addition to the hypothalamus. Immunoelectron microscopic analysis revealed the presence of synaptoid connections of immunoreactive fibers on neuronal somata in the tectum. The function of the mesencephalic system in the urodele seems to be sensory integration, suggesting that the orexin-A nervous system is associated with the modulation of sensory inputs. Orexin-A immunoreactive puncta were also observed on catecholaminergic and serotonergic somata. In view of the restricted somatic distribution in the hypothalamus, wide distribution of fibers throughout the central nervous system (CNS), and intimate association with monoaminergic somata, the orexin nervous system in the axolotl CNS is similar to those of other vertebrates, suggesting that this system is essential for brain functions throughout vertebrates.     

Carnosine, nerve growth factor receptor and tyrosine hydroxylase expression during the ontogeny of the rat olfactory system.

The localizations of carnosine, nerve growth factor (NGF) receptor and tyrosine hydroxylase (TH) were studied in the embryonic and postnatal rat olfactory bulb and epithelium by means of single- and double-immunostaining methods. Tyrosine hydroxylase ontogeny was also evaluated at the mRNA level by in situ hybridization. All these molecules were expressed in the olfactory bulb but with different developmental patterns and cellular localization: carnosine immunoreactivity is seen from embryonic day 17 in primary olfactory neurons scattered in the nasal cavity and in fibres projecting from them to the olfactory bulb. Nerve growth factor-receptor immunoreactivity associated with small glial-like cells is visible in some glomeruli starting from the second day of postnatal life. At postnatal day 10 NGF-receptor immunoreactivity is extended to all glomeruli. Periglomerular neurons expressing TH mRNA and protein are present prenatally and their number sharply increases during the early postnatal development. Double-staining methods show that TH and NGF-receptor immunoreactivity do not overlap in cell bodies and processes. In addition, NGF-receptor immunoreactivity is not colocalized with carnosine. These findings definitely exclude NGF-receptor expression in periglomerular and primary olfactory neurons, suggesting that at least part of NGF-receptor expression in the olfactory bulb is associated with glial cells. In addition, they provide the first immunohistochemical data on carnosine ontogeny and confirm at the mRNA level previous studies on the ontogeny of TH protein.     

一氧化氮合成酶阳性神经元在大鼠前脑的分布

用NADPH—d组织化学方法观察一氧化氮合成酶阳性神经元在大鼠前脑结构的分布和形态,结果显示在大脑皮质、纹状体、嗅球、杏仁核、基底前脑和下丘脑有较多一氧化氮合成酶神经元分布,这些神经元大多显示了Golgi样染色外观,它们尚不能与任何已知的神经递质类型神经元单一相对应.皮质、嗅球、纹状体和Calleja氏岛分别含有中等密度和密集的一氧化氮合成酶阳性纤维,一氧化氮合成酶阳性纤维较细,带有小的或中等大小的膨体,相互编织成疏密不等的纤维网.     

含Calbindin-D28K mRNA的神经元在大鼠前脑中的分布—原位杂交组织化学法观察

本实验应用原位杂交组织化学技术,利用同位素标记的寡核苷酸探针,对大鼠前脑含Calbindin-D28 K mRNA的神经元的分布状况进行了详细的观察。结果发现在不同脑区或核团中,标记神经元的数量和标记强度各不相同。某些部位含许多强阳性神经元,如:前嗅核、大脑皮质、尾壳核、缰核、下丘脑、齿状回及中脑和杏仁复合体中的部分核团;然而,在另外一些脑区中,标记细胞呈中等阳性,如:嗅球的球旁细胞、盖带、梨状区内核、海马的CA1区中的锥体细胞层以及丘脑和杏仁核复合体中的部分核团。少数脑区中的标记细胞呈弱阳性,且数量较少,如;嗅结节、隔区、斜角带核等。这些结果表明含Calbindin-D28K mRNA的神经元在大鼠前脑中具有区域特异性分布特点,从而提示Calbindin-D28K在神经系统中的某些部位可能具有重要的作用。     

Nerve growth factor receptor is associated with cholinergic neurons of the basal forebrain but not the pontomesencephalon

Sequential immunohistochemical demonstration of nerve growth factor receptor and cholinergic acetyltransferase on the same tissue section in the rat revealed that approximately 92% of all cholinergic neurons in the basal forebrain possessed that receptor. Only 0.9% of the neurons demonstrating nerve growth factor receptor in the basal nuclear complex lacked the cholinergic synthetic enzyme, and a similarly small percentage of cholinergic cells, 7.1%, were choline acetyltransferase-positive but nerve growth factor receptor-negative. Affiliation of nerve growth factor receptor with structural entities morphologically indistinguishable from those demonstrating choline acetyltransferase on separate but corresponding tissue sections was also observed in the telencephalic fiber tracts and terminal fields of basal forebrain cholinergic neurons, including cholinergic puncta in the reticular nucleus of the thalamus. Nerve growth factor receptor was not found in association with choline acetyltransferase-positive somata of the pedunculopontine and laterodorsal tegmental nuclei, however, nor were fibers immunoreactive for nerve growth factor receptor observed originating from those cell bodies. These results suggest that nerve growth factor receptor, which is probably synthesized in cholinergic basal forebrain somata and transported throughout their dendritic and axonal arbors, has a physiologic role in those cells in the adult nervous system. This does not appear to be the case for phenotypically similar neurons of the pontomesencephalotegmental cholinergic complex.     

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.     

Localization of chick retinal visinin-like immunoreactivity in the rat forebrain and diencephalon

The present study is an examination, using an indirect immunofluorescence method, of the distribution of visinin, a 24,000 dalton peptide, in the rat forebrain and diencephalon. Immunoreactive structures were localized in the neuronal elements showing an uneven distribution. Immunoreactive neurons were found in the olfactory bulb, anterior olfactory nucleus, cerebral cortex, amygdaloid complex, ventral portion of the nucleus caudatus putamen, septal area, nucleus accumbens, nucleus paratenialis, nucleus rhomboideus, nucleus reuniens, nucleus paraventricularis hypothalami, nucleus supraopticus, nucleus anterior hypothalami, preoptic area, hypothalamic periventricular nucleus, nucleus mammillaris medialis, medial habenular nucleus, zona incerta, nucleus lateralis thalami, nucleus tractus optici and gyrus dentatus. Immunoreactive fibers were observed in the above areas, particularly near the labelled cells, forming fiber plexuses of varying density. In addition, dense plexuses were also seen in the globus pallidus, anteroventral nucleus of the thalamus, substantia nigra and hippocampus. In the former three structures, no labelled cells were present and in the latter, a few scattered neurons were found, indicating that these fibers originate from extrinsic sources.     

Transneuronal transport of peroxidase-conjugated wheat germ agglutinin (WGA-HRP) from the olfactory epithelium to the brain of the adult rat

Summary The sensory neurons of the olfactory epithelium, as a consequence of their odor detection function, contact both the external environment and the central nervous system. The possibility that substances applied to the epithelium might reach the central nervous system was investigated by the intranasal application of peroxidase-conjugated wheat germ agglutinin (WGA-HRP). WGA-HRP was transported through olfactory receptor axons to the glomerulus of the olfactory bulb. Reaction product was localized electron microscopically to tubulovesicular profiles and dense bodies in sensory axons. Evidence of transneuronal transport was indicated by reaction product localized in dense bodies in dendrites postsynaptic to receptor cell axons. Periglomerular, tufted and mitral cells in the olfactory bulb also were transneuronally labeled. Anterograde transneuronal labeling occured in the olfactory tubercle, piriform cortex and surrounding the lateral olfactory tract. Retrograde transneuronal label was found in neurons of the basal forebrain with the largest number of perikarya in the lateral nucleus of the horizontal limb of the diagonal band, a major source of cholinergic afferents to the olfactory bulb. These data suggest that substances, specifically those which bind to receptors, are transported from the olfactory receptor neurons in the nasal epithelium to the brain. Thus, the olfactory system may provide a route of entry for exogenous substances to the basal forebrain.Abbreviations AC anterior commissure - CC corpus callosum - CI internal capsule - CP caudate putamen - DBB diagonal band of Broca - FX fornix - GP globus pallidus - IC island of Callelae - LV lateral ventricle - MS medial septum - OC optic chiasm - PIR piriform cortex - RF rhinal fissure - SON supraoptic nucleus - SCN suprachiasmatic nucleus - SM stria medullaris - ST stria terminalis - TOL lateral olfactory tract - TUO olfactory tubercle - III third ventricle     

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.     

Atrial natriuretic polypeptide: topographical distribution in the rat brain by radioimmunoassay and immunohistochemistry

The widespread distribution of neurons containing alpha-atrial natriuretic polypeptide-like immunoreactivity in the rat brain was demonstrated using radioimmunoassay and immunohistochemistry in conjunction with specific antisera. The highest concentrations of alpha-atrial natriuretic polypeptide-like immunoreactivity were in the hypothalamus and septum, with low but still appreciable concentrations in the mesencephalon, cerebral cortex, olfactory bulb and thalamus by radioimmunoassay. Immunohistochemical studies clearly showed that the perikarya of immunoreactive neurons are most prevalent in the ventral part of the lateral septal nucleus, periventricular preoptic nucleus, bed nucleus of the stria terminalis, periventricular and dorsal parts of the paraventricular hypothalamic nucleus, ventromedial nucleus, dorsomedial nucleus, arcuate nucleus, median mamillary nucleus, supramamillary nucleus, zona incerta, medial habenular nucleus and the periaqueductal grey matter. Scattered neurons were seen in the cingulate cortex, endopiriform nucleus, lateral hypothalamic area, and pretectal and dorsal thalamic areas. In addition to the areas mentioned above, high concentrations of immunoreactive varicose fibers were seen in the glomerular layer of the olfactory bulb, external layer of the median eminence, central to paramedian parts of the interpeduncular nucleus and the paraventricular hypothalamic nucleus. The globus pallidus, medial and central amygdaloid nuclei, dorsal raphe, dorsal parabrachial nucleus, locus coeruleus, vagal dorsal motor nucleus, solitary nucleus and some circumventricular organs, including the subfornical organ and organum vasculosum laminae terminalis, contained considerable numbers of immunoreactive varicose fibers. In dehydrated rats and homozygous Brattleboro rats, the pattern of alpha-atrial natriuretic polypeptide-immunoreactive neurons and varicose fibers was qualitatively similar to that seen in normal conditioned rats. This study gives an atlas of the distribution of the alpha-atrial natriuretic polypeptide-containing neuronal system in the rat brain and provides the groundwork for studying the influence of this new peptide on various brain functions.     

Distribution of insulin receptor-like immunoreactivity in the rat forebrain

Previous studies have suggested that insulin may play a role in the hormonal regulation of neurotransmitter metabolisms within the central nervous system. In order to provide additional information to support this hypothesis, we examined the distribution of insulin receptors within the forebrain of adult male rats. Insulin receptors were localized by immunocytochemistry, using an antibody directed against the carboxy-terminus of the beta-subunit of the insulin receptor. The antibody specificity was tested by immunoprecipitation of brain insulin receptors with antiserum and the purity of the receptor-antibody preparation was determined using hormone binding-assays with radiolabeled insulin and insulin-like growth factor-l. Insulin receptor-like immunoreactivity was found in a widespread, but selective, distribution on neurons throughout the rat forebrain. Double-labeling with glial fibrillary acidic protein did not demonstrate any detectable insulin receptor-like immunoreactivity on glial cells. Areas with the highest density of insulin receptor-like immunoreactivity were found in the olfactory bulbs, hypothalamus and median eminence, medial habenula, subthalamic nucleus, subfornical organ, CA 1/2 pyramidal cell layer of the hippocampus and piriform cortex. Double-staining of hypothalamic sections with somatostatin and vasopressin antisera revealed insulin receptor-like immunoreactivity on a subpopulation of somatostatin neurons in the periventricular region and on vasopressin neurons in the supraoptic nucleus. A moderately dense insulin receptor-like immunoreactivity was observed in layers II-IV of cerebral cortex, medial amygdala, reticular thalamic nucleus, zona incerta, and preoptic and septal regions, whereas a low density of insulin receptor-like immunoreactive neurons was found in basolateral amygdala and most thalamic regions. The basal ganglia and most parts of the thalamus were almost devoid of insulin receptor-like immunoreactivity. Our findings provide morphological support for a direct action of insulin on selected regions of the rat forebrain and suggest that the insulin receptor may modulate synaptic transmission or the release of neurotransmitters and peptide hormones in the CNS.     

Small cholinergic neurons within fields of cholinergic axons characterize olfactory-related regions of rat telencephalon.

Small immunoreactive cholinergic neurons were detected in the main and accessory olfactory bulbs of the rat with choline acetyltransferase immunocytochemistry. Such cells were also found in additional forebrain regions that received direct efferent innervation from the main olfactory bulb, such as the anterior olfactory nucleus, two subdivisions of the olfactory amygdala (nucleus of the lateral olfactory tract and anterior cortical nucleus), and the cortical-amygdaloid transition zone. Cholinergic neurons located in these olfactory-related regions were similar to each other morphologically and to those previously described by other investigators in the cerebral cortex, the hippocampus, and the basolateral amygdala. Somal measurements indicated that choline acetyltransferase-positive cells in olfactory-related regions were all essentially the same size, measuring 13-14 by 8-9 microns in major and minor diameters, respectively. In addition, these small cells were commonly bipolar in form with thin, smooth dendrites, and such characteristics have generally been associated with intrinsic, local circuit neurons in the forebrain. Depending on their location, however, these small cholinergic neurons differed from each other with regard to their frequency and dendritic orientation within planar sections. Choline acetyltransferase-immunoreactive cells in most cortical regions were relatively numerous and usually exhibited long, planar dendrites oriented perpendicularly to the pial surface. In contrast, dendrites of cholinergic neurons found in "cortical-like" regions (e.g. olfactory bulbs or nucleus of the lateral olfactory tract) were relatively sparse in number and appeared to be distinctly non-planar and randomly oriented. Despite these differences, the small choline acetyltransferase-positive cells had many features in common, including their distribution within forebrain regions that contained substantial terminal networks of choline acetyltransferase-positive axons thought to be derived primarily from the basal forebrain complex. In the rat, at least, the presence of small cholinergic interneurons within forebrain regions innervated by the large cholinergic projection neurons of the basal forebrain seems to be developing as a general principle of telencephalic organization. However, differences in both the size and the distribution of the terminal fields derived from each source imply a functional diversity between the intrinsic and extrinsic cholinergic systems of the forebrain.     

The immunocytochemical localization of somatostatin-containing neurons in the rat central nervous system

Somatostatin-containing neurons in the rat central nervous system were localized by immunocytochemical methods. The detection of somatostatin-like immunoreactivity was facilitated by (1) the use of brains from colchicine-treated rats, (2) the proteolytic pretreatment of sections with pronase and (3) a ‘double-bridge’ immunoperoxidase staining technique. In addition to the known distribution of somatostatin-like immunoreactivity we also observed immunoreactive perikarya in the following regions: the anterior olfactory nucleus, some areas of the preoptic and hypothalamic regions, the claustrum, the periaqueductal gray, the locus ceruleus, the central gray substance, the lateral parabrachial nucleus, the nucleus of the lateral lemniscus, the nucleus ambiguus, the spinal trigeminal nucleus, the nucleus of the solitary tract and various areas of the reticular formation. Immunoreactive neuronal processes were also observed in several major tracts of the brain, including the stria terminalis, the fornix and the medial forebrain bundle.Our results indicate that somatostatin-containing neurons may occur both as interneurons in some areas of the central nervous system and as projection neurons in others. The widespread but selective distribution of these neurons suggests that somatostatin is not only a hypothalamic regulator of neuroendocrine function, but may also function as a major neuromodulator mediating a variety of functions throughout the central nervous system.     

Histamine-immunoreactive nerve fibers in the rat brain

A new immunohistochemical method that utilizes carbodiimide as a tissue fixative was applied to study the distribution of histamine-immunoreactive neuronal fibers and terminals in the rat brain. Immunoreactive fibers were observed in almost all major regions of the brain. They were most numerous in the different hypothalamic nuclei. Dense networks of immunoreactive fibers were also seen in the medial septum, nucleus of the diagonal band and ventral tegmental area. A moderate density of fibers was seen throughout the cerebral cortex, in some parts of the olfactory bulb and tubercle, bed nucleus of the stria terminalis, amygdala, basal parts of the hippocampus, inferior and superior colliculi, substantia nigra, lateral and medial parabrachial nucleus, and the nucleus of the solitary tract. Few histamine-immunoreactive fibers were seen in most parts of the caudate putamen, most thalamic nuclei, most pontine and ventral medullary nuclei. Histamine-immunoreactive neuronal cell bodies were found exclusively in the tuberomammillary nucleus, in agreement with previous reports. The results provide evidence for a widespread distribution of histamine-containing nerve fibers and terminals in the rat brain. Although immunohistochemical localization of histamine does not give direct evidence of a functional role of histamine in any brain area, this distribution suggests involvement in functions of the limbic system including the septal nuclei, hypothalamus and amygdala. The relatively dense histamine-immunoreactive fiber networks in the colliculi and dorsal cochlear nucleus indicate that this amine may play a role in visual functions and hearing. The paucity of immunoreactive fibers in the pontine and medullary areas suggests that the caudal projections originating from the tuberomammillary complex are minor ones compared to the major rostral projections. Several fiber projections originating from the tuberomammillary complex could be deduced from serial frontal, sagittal and horizontal sections. They contained fibers that crossed the midline at several levels of the brain. The results provide information on the target areas of the histaminergic neurons and form a basis for the examination of cellular contracts between the histaminergic neurons and other cells.     

Immunohistochemical localization of insulin receptors and phosphotyrosine in the brainstem of the adult rat.

Previous studies have demonstrated that insulin receptors are widely distributed throughout areas of the forebrain in the adult rat that are involved in modulating neuroendocrine functions and feeding behaviour. In addition, a recent investigation showed that there is a good correlation between the presence of the insulin receptor and phosphotyrosine-containing proteins in these regions, indicating a possible functional activity of insulin receptors in vivo. It is unknown whether neural connections between specific brainstem nuclei to forebrain regions may also be under direct regulation of insulin or related factors. In order to test this possibility, the distribution of insulin receptors and phosphotyrosine was mapped throughout the hindbrain of the adult rat by immunocytochemistry, using specific antibodies against the beta-subunit of the insulin receptor as well as against phosphotyrosine. Both markers showed a high degree of overlap throughout numerous distinct anatomical regions of the hindbrain. In the mesencephalon, insulin receptor and phosphotyrosine-positive neurons were found in the precommissural nucleus, the lateral and dorsal part of the central gray, the mammillary bodies and the interpeduncular nucleus. In addition, immunoreactivity was found in the subependymal layer around the aqueduct along fibres and nerve cells possibly contacting the cerebrospinal fluid. In the pons and medulla, dense immunoreactivity was seen in the lateral superior olive, nucleus of the solitary tract, spinal trigeminal nucleus and nucleus ambiguous. Scattered cells were found in the pontine and vestibular nuclei, as well as in the reticular formation. The cerebellum contained moderately dense immunoreactivity in the granule cell and molecular cell layer of the cortex, as well as in the deep cerebellar nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)     

Localization of N-acetylaspartylglutamate-like immunoreactivity in selected areas of the rat brain

N-acetylaspartylglutamate (NAAG) was detected immunohistochemically in the rat brain using an antiserum which recognizes carbodiimide-fixed NAAG. NAAG-like immunoreactivity is described in 5 areas of the brain; olfactory bulb, septal nuclear area, lateral geniculate nucleus, superior colliculus and the entorhinal cortex/hippocampal formation. Mitral cells of the olfactory bulb and neurons concentrated in the medial septum were densely immunostained. A dense population of immunoreactive puncta was found in the superior colliculus and lateral geniculate nucleus (LGN). The LGN also contained immunoreactive neurons. The entorhinal cortex contained numerous immunoreactive cells in layers II-III while the hippocampus had few neurons that were NAAG-positive.