SCN2B in the Rat Trigeminal Ganglion and Trigeminal Sensory Nuclei

The beta-2 subunit of the mammalian brain voltage-gated sodium channel (SCN2B) was examined in the rat trigeminal ganglion (TG) and trigeminal sensory nuclei. In the TG, 42.6 % of sensory neurons were immunoreactive (IR) for SCN2B. These neurons had various cell body sizes. In facial skins and oral mucosae, corpuscular nerve endings contained SCN2B-immunoreactivity. SCN2B-IR nerve fibers formed nerve plexuses beneath taste buds in the tongue and incisive papilla. However, SCN2B-IR free nerve endings were rare in cutaneous and mucosal epithelia. Tooth pulps, muscle spindles and major salivary glands were also innervated by SCN2B-IR nerve fibers. A double immunofluorescence method revealed that about 40 % of SCN2B-IR neurons exhibited calcitonin gene-related peptide (CGRP)-immunoreactivity. However, distributions of SCN2B- and CGRP-IR nerve fibers were mostly different in facial, oral and cranial structures. By retrograde tracing method, 60.4 and 85.3 % of TG neurons innervating the facial skin and tooth pulp, respectively, showed SCN2B-immunoreactivity. CGRP-immunoreactivity was co-localized by about 40 % of SCN2B-IR cutaneous and tooth pulp TG neurons. In trigeminal sensory nuclei of the brainstem, SCN2B-IR neuronal cell bodies were common in deep laminae of the subnucleus caudalis, and the subnuclei interpolaris and oralis. In the mesencephalic trigeminal tract nucleus, primary sensory neurons also exhibited SCN2B-immunoreactivity. In other regions of trigeminal sensory nuclei, SCN2B-IR cells were very infrequent. SCN2B-IR neuropil was detected in deep laminae of the subnucleus caudalis as well as in the subnuclei interpolaris, oralis and principalis. These findings suggest that SCN2B is expressed by various types of sensory neurons in the TG. There appears to be SCN2B-containing pathway in the TG and trigeminal sensory nuclei.     

Localization of proopiomelanocortin (POMC) immunoreactive neurons in the forebrain of the pig

The distribution of proopiomelanocortin (POMC)-immunoreactive neurons was examined in the forebrains of nine sexually mature female pigs by indirect biotin-avidin horseradish peroxidase immunocytochemistry. Primary antiserum against ovine beta-endorphin (Bioflex #BF-EP-3-1) yielded positive staining of neuronal perikarya and processes. Adjacent control sections treated either with primary antiserum preabsorbed with beta-endorphin or substituted with normal rabbit serum lacked specific staining. POMC-immunoreactive cells were located in the anterior and intermediate lobe of the pituitary gland. POMC-immunoreactive perikarya were located in the arcuate nucleus and periarcuate area. The pituitary stalk/median eminence contained sparsely distributed POMC-immunoreactive fibers, which were confined to the zona interna. POMC-immunoreactive fibers were located in the arcuate nucleus and extended rostrally from the arcuate nucleus into the telencephalon coursing adjacent to the wall of the third ventricle as well as through the anterior hypothalamus, suprachiasmatic, supraoptic nuclei and preoptic areas to the nucleus accumbens, diagonal band of Broca, olfactory tubercle, bed nucleus of the stria terminalis and the ventro-lateral aspect of the septum. Caudal projections extended along the wall of the third ventricle to the level of the mammillary bodies and also coursed dorsally, passing through the periventricular, paraventricular, and dorsal medial nuclei of the hypothalamus to the midline thalamic nuclei and habenular nucleus. Lateral projections extended from the arcuate nucleus along the dorsal aspect of the optic tract and terminated in the amygdaloid complex. The distribution of POMC-immunoreactive perikarya and fibers is similar to that of the luteinizing hormone-releasing hormone (LHRH) fiber network. Therefore the opportunities exist, anatomically, for interactions between the POMC and the LHRH systems.     

Stereological evaluation and Golgi study of the sexual dimorphisms in the volume,cell numbers,and cell size in the medial preoptic nucleus of the rat

The medial preoptic nucleus (MPN) and the sexually dimorphic nucleus of the preoptic area (SDN-POA) stand out as prominent sexually dimorphic cell groups of the rat brain. However, quantitative data on sex-related differences in these nuclei in the adult rat are confined to their volume. We have used stereological methods and Golgi-impregnated material to examine whether, in young adult rats, the sexual dimorphism in the volume of the MPN, including its divisions, and of the SDN-POA, reflect similar differences in the number and size of their neurons. We found that the total number of neurons in all MPN divisions is higher and the mean somatic volume larger in males than in females. In addition, the total dendritic length of MPN neurons is greater, but the dendritic spine density is smaller, in males than in females. Likewise, in the SDN-POA the total number and size of its neurons is greater in males than in females. The sex differences in all quantitative parameters evaluated accounted for the larger volume of the MPN and SDN-POA in males relative to females. In addition, the MPN neuropil also displays sex-related differences in its volume, and these differences closely match those detected for the volume of each MPN division. It deserves to be emphasised that the numerical density of neurons was the only parameter found to be significantly higher in females than in males in all MPN divisions and in the SDN-POA. Our results show that the MPN and the SDN-POA display sex differences in the volume, total number of neurons, and size of neuronal cell bodies and dendritic trees. Furthermore, they also indicate that the neuropil is critical for the establishment of sexual dimorphism in the size of the MPN.     

Anatomical relationship between neuropeptide-containing fibers and efferent vagal neurons projecting to the rat corpus.

Injections of the retrograde tracers into the posterior surface of the stomach at the greater curvature resulted in labelling of the right half of the dorsal motor nucleus of the vagus. Whereas injections into the anterior and posterior surfaces of the corpus resulted in bilateral labelling in the medulla. Immunocytochemical staining of the labelled sections using antisera to substance P was confined to a dense network of fibers within the dorsal motor nucleus of the vagus and the nucleus tractus solitarius with no cell bodies being detected. Calcitonin gene-related peptide-immunoreactivity was detected in nerve fibers in the nucleus tractus solitarius and cell bodies of the hypoglossal nucleus. Finally, neuropeptide Y-immunoreactivity was confined to nerve fibers within the vagal complex. Of the neurons labelled by the retrograde tracers injected into the corpus all were in close spatial contact with fibers containing substance P-immunoreactivity. A smaller number were associated with neuropeptide Y-containing fibers with a few adjacent to calcitonin gene-related peptide-immunoreactive fibers. These results indicate that substance P and neuropeptide Y may directly regulate efferent neurons controlling gastric motility and acid secretion. Calcitonin gene-related peptide, however, is unlikely to directly modulate the cell bodies of the neurons in the dorsal motor nucleus but may modulate the dendrites from these neurons in the nucleus tractus solitarius.     

Neural interaction of gonadotropin-regulating hormone immunoreactive neurons and the suprachiasmatic nucleus with the paraventricular organ in the Japanese grass lizard (Takydromus tachydromoides)

Our previous study demonstrated that the paraventricular organ (PVO) in the hypothalamus of the Japanese grass lizard (Takydromus tachydromoides) showed immunoreactivity against the light signal-transducing G-protein, transducin. This finding suggested that the PVO was a candidate for the deep-brain photoreceptor in this species. To understand functions of the PVO, we investigated distributions of transducin, serotonin, gonadotropin-releasing hormone (GnRH), and gonadotropin-inhibitory hormone (GnIH) in the lizard's brain. We immunohistochemically confirmed co-localization of transducin and serotonin in PVO neurons that showed structural characteristics of cerebrospinal fluid (CSF)-contacting neurons. GnRH-immunoreactive (ir) cells were localized in the posterior commissure and lateral hypothalamic area. Some of the serotonin-ir fibers extending from the PVO to the lateral hypothalamic area contacted the GnRH-ir cell bodies. GnIH-ir cells were localized in the nucleus accumbens, paraventricular nucleus, and upper medulla, and GnIH-ir fibers from the paraventricular nucleus contacted the lateral processes of serotonin-ir neurons in the PVO. In addition, we found that serotonin-ir fibers from the PVO extended to the suprachiasmatic nucleus (SCN), and the retrograde transport method confirmed the PVO projections to the SCN. These findings suggest that the PVO, by means of innervation mediated by serotonin, plays an important role in the regulation of pituitary function and the biological clock in the Japanese grass lizard.     

Dynamic alterations in luteinizing hormone-releasing hormone (LHRH) neuronal cell bodies and terminals of adult rats

Summary 1. The decapeptide lueteinizing hormone-releasing hormone (LHRH) is synthesized in neuronal cell bodies diffusely distributed across the basal forebrain and is secreted from neuronal terminals in the median eminence. Once secreted, LHRH enters the portal vessels and is then transported to the anterior pituitary, where it modulates the synthesis and secretion of gonadotropins, which are essential to gonadal function and reproduction.2. Because of the difficulties encountered in studying these diffusely distributed neurons, we have developed strategies which combine immunocytochemistry and computer-assisted techniques to examine individual LHRH neuronal cell bodies, as well as the entire population of LHRH neurons from the diagonal band of Broca to the mammillary bodies. In addition, we have examined LHRH neuronal terminals in the median eminence using computer-assisted imaging techniques to examine individual terminals by electron microscopy or across all rostral-caudal regions of the median eminence by light microscopy. In our most recent studies using confocal microscopy, we have examined the relationships of LHRH terminals to glial processes.3. These studies reveal a very dynamic system of LHRH neuronal cell bodies and terminals. The population of neurons in which LHRH can be detected varies as a function of time after gonadectomy, during the estrous cycle, and during the preovulatory surge of LH during the afternoon of proestrus. Dynamic changes are also observed in LHRH terminals in the median eminence as a function of time after gonadectomy and in specific rostral-caudal regions of the median eminence during the preovulatory surge of LH. Finally, confocal microscopy reveals that LHRH terminals are prevented from contacting the basal lamina of the brain by glial end-feet.4. We are currently examining the hypothesis that these relationships change as a function of endocrine milieu and, therefore, participate in the modulation of LHRH secretion. Ongoing studies focus on defining the sites of action and synergy of multiple sources of regulation of LHRH secretion and their relative importance to ensuring reproductive success.     

Effects of Neuropeptide Y (NPY) on the release of anterior pituitary hormones in the rat

Neuropeptide Y (NPY) has been recently localized in several hypothalamic nuclei in the mammalian brain. In order to investigate the possible role of NPY on neuroendocrine function, we have investigated the effects of the peptide on the release of anterior pituitary hormones in the rat. Both intravenous (300 μg) or intraventricular (2 to 15 μg) injection of NPY produced in gonadectomized male rats a significant and long-lasting decrease of plasma LH levels. A short duration stimulating effect on prolactin plasma levels was also observed after the intravenous but not after the intraventricular injection of NPY. Plasma levels of the other pituitary hormones were not significantly modified after NPY injection. When incubated in vitro with anterior pituitary cells in monolayer culture, NPY produced no significant change in release of pituitary hormones. Thus NPY seems to exert a selective effect on LH release. Since this effect can be observed after both intravenous and intraventricular injection, it might be hypothesized that NPY could affect LHRH release in two areas which lack blood-brain barrier: the organum vasculosum of the lamina terminalis (OVLT) which contains LHRH cell bodies and NPY fibers and the median eminence which contains both LHRH and NPY fibers. The effect on prolactin release needs to be carefully evaluated in different experimental conditions.     

The thalamic paraventricular nucleus relays information from the suprachiasmatic nucleus to the amygdala: A combined anterograde and retrograde tracing study in the rat at the light and electron microscopic levels

The relationship between efferents of the hypothalamic suprachiasmatic nucleus (SCN) and neurons of the thalamic paraventricular nucleus (PVT) projecting to the amygdala was investigated in the rat using tract tracing in light and electron microscopy. Biotinylated dextran amine was used to label anterogradely SCN efferents. These fibers were found to reach the thalamic midline, terminating in PVT, through three pathways: anterodorsally through the preoptic region, dorsally through the periventricular hypothalamus, and through the contralateral medial hypothalamic and preoptic areas after crossing the midline in the optic chiasm. Preterminal and terminal-like elements labeled from the SCN were distributed throughout the rostrocaudal extent of PVT, with an anteroposterior gradient of density. Labeled terminal elements were densest in the dorsal portion of PVT beneath the ependymal lining and some of them entered the ependyma. Anterograde tracing of SCN fibers was combined with injections of retrograde tracers in the amygdala. Numerous retrogradely labeled cell bodies were seen throughout PVT, with a prevalence in its anterodorsal portion. Overlap was detected between puncta labeled from the SCN and retrogradely labeled neurons, especially in the anterodorsal sector of PVT, where numerous puncta were in close apposition to thalamo-amygdaloid cells. Electron microscopy revealed that boutons labeled from the SCN established synaptic contacts with dendritic profiles of PVT neurons labeled from the amygdala. The findings demonstrate that information processed in the biological clock is conveyed to the amygdala through PVT, indicating that this nucleus plays a role in the transfer of circadian timing information to the limbic system.     

Localization of immunoreactive lamprey gonadotropin-releasing hormone in the rat brain

A highly specific antiserum against lamprey gonadotropin-releasing hormone (GnRH) was used to localize 1-GnRH in areas of the rat brain associated with reproductive function. Immunoreactive 1-GnRH-like neurons were observed in the ventromedial preoptic area (POA), the region of the diagonal band of Broca and the organum vasculosum lamina terminalis, with fiber projections to the rostral wall of the third ventricle and the organum vasculosum lamina terminalis. Another population of 1-GnRH-like neurons was localized in the dorsomedial and lateral POA, with nerve fibers projecting caudally and ventrally to terminate in the external layer of the median eminence. Other fibers apparently projected caudally and circumventrically to terminate around the cerebral aqueduct in the mid-brain central gray. By using a highly specific antiserum directed against mammalian luteinizing hormone-releasing hormone (m-LHRH), the localization of the LHRH neuronal system was compared to that of the 1-GnRH system. There were no LHRH neurons in the dorsomedial or the lateral region of the POA that contained the 1-GnRH neurons. As expected, there was a large population of LHRH neurons in the ventromedial POA associated with the diagonal band of Broca and organum vasculosum lamina terminalis. In both of these regions, there were many more LHRH neurons than 1-GnRH neurons and the LHRH neurons extended more dorsally and laterally than the 1-GnRH neurons. The LHRH neurons seemed to project to the median eminence in the same areas as those that were innervated by the 1-GnRH neurons. Absorption studies indicated that 1-GnRH cell bodies were eliminated by adding 1 microg of either 1-GnRH-I or 1-GnRH-III, but not m-LHRH to the antiserum before use. Fibers were largely eliminated by the addition of 1 microg 1-GnRH-III to the antiserum. No chicken GnRH-II neurons or nerve fibers could be visualized by immunostaining. Because the antiserum recognized GnRH-I and GnRH-III equally, we have visualized an 1-GnRH system in rat brain. The results are consistent with the presence of either one or both of these peptides within the rat hypothalamus. Because 1-GnRH-I has only weak nonselective gonadotropin-releasing activity, whereas 1-GnRH-III is a highly selective releaser of follicle-stimulating hormone, and because 1-GnRH neurons are located in areas known to control follicle-stimulating hormone release selectively, our results support the hypothesis that 1-GnRH-III, or a closely related peptide, may be mammalian follicle-stimulating hormone-releasing factor.     

Somatostatin-like immunoreactivity in the amygdala of the pig

The distribution and morphology of neurons containing somatostatin (SOM) was investigated in the amygdala (CA) of the pig. The SOM-immunoreactive (SOM-IR) cell bodies and fibres were present in all subdivisions of the porcine CA, however, their number and density varied depending on the nucleus studied. The highest density of SOM-positive somata was observed in the layer III of the cortical nuclei, in the anterior (magnocellular) part of the basomedial nucleus and in the caudal (large-celled) part of the lateral nucleus. Moderate to high numbers of SOM-IR cells were also observed in the medial and basolateral nuclei. Many labeled neurons were also consistently observed in the lateral part of the central nucleus. In the remaining CA regions, the density of SOM-positive cell bodies varied from moderate to low. In any CA region studied SOM-IR neurons formed heterogeneous population consisting of small, rounded or slightly elongated cell bodies, with a few poorly branched smooth dendrites. In general, morphological features of these cells clearly resembled the non-pyramidal Golgi type II interneurons. The routine double-labeling studies with antisera directed against SOM and neuropeptide Y (NPY) demonstrated that a large number of SOM-IR cell bodies and fibers in all studied CA areas contained simultaneously NPY. In contrast, co-localization of SOM and cholecystokinin (CCK) or SOM and vasoactive intestinal polypeptide (VIP) was never seen in cell bodies and fibres in any of nuclei studied. In conclusion, SOM-IR neurons of the porcine amygdala form large and heterogeneous subpopulation of, most probably, interneurons that often contain additionally NPY. On the other hand, CCK- and/or VIP-IR neurons belonged to another, discrete subpopulations of porcine CA neurons.     

大鼠脑内代谢型谷氨酸受体5亚型(mGluR5)定位分布的免疫细胞化学研究

本研究用免疫细胞化学技术观察了大鼠脑内参与兴奋性突触传递的代谢型谷氨酸受体5亚型(mGluR5)的精确定位分布.mGluR5阳性浓染的神经元胞体和纤维密集地分布于大脑皮质浅层、嗅球、伏核、尾壳核、前脑基底部、隔区、苍白球、腹侧苍白球、海马CA1和CA2区、下丘中央核、被盖背侧核和三叉神经脊束核尾侧亚核浅层;淡染而稀疏的mGluR5阳性神经元胞体和纤维见于屏状核、终纹床核、杏仁中央核、丘脑部分核团、上丘浅灰质层、外侧丘系背侧核和延髓中央灰质.     

Localization of immunoreactive lamprey gonadotropin-releasing hormone in the rat brain

A highly specific antiserum against lamprey gonadotropin-releasing hormone (GnRH) was used to localize 1-GnRH in areas of the rat brain associated with reproductive function. Immunoreactive 1-GnRH-like neurons were observed in the ventromedial preoptic area (POA), the region of the diagonal band of Broca and the organum vasculosum lamina terminalis, with fiber projections to the rostral wall of the third ventricle and the organum vasculosum lamina terminalis. Another population of 1-GnRH-like neurons was localized in the dorsomedial and lateral POA, with nerve fibers projecting caudally and ventrally to terminate in the external layer of the median eminence. Other fibers apparently projected caudally and circumventrically to terminate around the cerebral aqueduct in the mid-brain central gray. By using a highly specific antiserum directed against mammalian luteinizing hormone-releasing hormone (m-LHRH), the localization of the LHRH neuronal system was compared to that of the 1-GnRH system. There were no LHRH neurons in the dorsomedial or the lateral region of the POA that contained the 1-GnRH neurons. As expected, there was a large population of LHRH neurons in the ventromedial POA associated with the diagonal band of Broca and organum vasculosum lamina terminalis. In both of these regions, there were many more LHRH neurons than 1-GnRH neurons and the LHRH neurons extended more dorsally and laterally than the 1-GnRH neurons. The LHRH neurons seemed to project to the median eminence in the same areas as those that were innervated by the 1-GnRH neurons. Absorption studies indicated that 1-GnRH cell bodies were eliminated by adding 1 microg of either 1-GnRH-I or 1-GnRH-III, but not m-LHRH to the antiserum before use. Fibers were largely eliminated by the addition of 1 microg 1-GnRH-III to the antiserum. No chicken GnRH-II neurons or nerve fibers could be visualized by immunostaining. Because the antiserum recognized GnRH-I and GnRH-III equally, we have visualized an 1-GnRH system in rat brain. The results are consistent with the presence of either one or both of these peptides within the rat hypothalamus. Because 1-GnRH-I has only weak nonselective gonadotropin-releasing activity, whereas 1-GnRH-III is a highly selective releaser of follicle-stimulating hormone, and because 1-GnRH neurons are located in areas known to control follicle-stimulating hormone release selectively, our results support the hypothesis that 1-GnRH-III, or a closely related peptide, may be mammalian follicle-stimulating hormone-releasing factor.     

Colocalization of neuropeptide Y (NPY)-like and FMRFamide-like immunoreactivities in the brain of the Atlantic salmon (Salmo salar)

Summary The colocalization of the peptides neuropeptide Y (NPY) and Phe-Met-Arg-Phe-NH₂ (FMRFamide) in the brain of the Atlantic salmon was investigated with double immunofluorescence labeling and peroxidase-antiperoxidase immunocytochemical techniques. Colocalization of NPY-like and FMRE amide-like immunoreactivities was observed in neuronal cell bodies and fibers in four brain regions: in the lateral and commissural nuclei of the area ventralis telencephali, in the nucleus ventromedialis thalami, in the laminar nucleus of the mesencephalic tegmentum, and in a group of small neurons situated among the large catecholaminergic neurons in the isthmal region of the brainstem. All cell bodies in these nuclei were immunoreactive to both NPY and FMRF. We consistently observed larger numbers of FMRF-immunoreactive than NPY-immunoreactive fibers. In the nucleus ventromedialis thalami NPY- and FMRFamide-like immunoreactivities were colocalized in cerebrospinal fluid (CSF)-contacting neurons. NPY-immunoreactive, but not FMRF-immunoreactive, neurons were found in the stratum periventriculare of the optic tectum, and at the ventral border of the nucleus habenularis (adjacent to the nucleus dorsolateralis thalami). Neurons belonging to the nucleus of the nervus terminalis were FMRF-immunoreactive but not NPY-immunoreactive. The differential labeling indicates, as do our cross-absorption experiments, that the NPY and FMRFamide antisera recognize different epitopes. Thus, it is probable that NPY-like and FMRFamide-like substances occur in the same neurons in some brain regions.     

Calcitonin gene-related peptide: detailed immunohistochemical distribution in the central nervous system

With the use of an antiserum generated in rabbits against synthetic human calcitonin gene-related peptide (CGRP) the distribution of CGRP-like immunoreactive cell bodies and nerve fibers was studied in the rat central nervous system. A detailed stereotaxic atlas of CGRP-like neurons was prepared. CGRP-like immunoreactivity was widely distributed in the rat central nervous system. CGRP positive cell bodies were observed in the preoptic area and hypothalamus (medial preoptic, periventricular, anterior hypothalamic nuclei, perifornical area, medial forebrain bundle), premamillary nucleus, amygdala medialis, hippocampus and dentate gyrus, central gray and the ventromedial nucleus of the thalamus. In the midbrain a large cluster of cells was contained in the peripeduncular area ventral to the medial geniculate body. In the hindbrain cholinergic motor nuclei (III, IV, V, VI, VII XII) contained CGRP-immunoreactivity. Cell bodies were also observed in the ventral tegmental nucleus, the parabrachial nuclei, superior olive and nucleus ambiguus. The ventral horn cells of the spinal cord, the trigeminal and dorsal root ganglia also contained CGRP-immunoreactivity. Dense accumulations of fibers were observed in the amydala centralis, caudal portion of the caudate putamen, sensory trigeminal area, substantia gelatinosa, dorsal horn of the spinal cord (laminae I and II). Other areas containing CGRP-immunoreactive fibers are the septal area, nucleus of the stria terminalis, preoptic and hypothalamic nuclei (e.g., medial preoptic, periventricular, dorsomedial, median eminence), medial forebrain bundle, central gray, medial geniculate body, peripeduncular area, interpeduncular nucleus, cochlear nucleus, parabrachial nuclei, superior olive, nucleus tractus solitarii, and in the confines of clusters of cell bodies. Some fibers were also noted in the anterior and posterior pituitary and the sensory ganglia. As with other newly described brain neuropeptides it can only be conjectured that CGRP has a neuroregulatory action on a variety of functions throughout the brain and spinal cord.     

Calbindin D-28K in the nucleus pretectalis superficialis parvicellularis of Salmo gairdneri: an immunocytochemical study.

The distribution of calbindin D-28K (CaBP28K) cell bodies and fibers in the nucleus pretectalis superficialis parvicellularis of the rainbow trout was studied using a monoclonal antibody and the avidin-biotin-peroxidase method. In this diencephalic nucleus a very high density of CaBP28K immunoreactive fibers was found. In addition, a high density of CaBP28K positive neurons was also observed. These neurons were small, showing one, two or three short and non-branching dendritic trunks. The distribution and orientation of the immunoreactive cell bodies in the nucleus pretectalis superficialis parvicellularis suggests that the neurons might be interneurons and/or projecting neurons.     

Neural interaction between galanin-like peptide (GALP)- and luteinizing hormone-releasing hormone (LHRH)-containing neurons

Galanin-like peptide (GALP), commonly known as an appetite-regulating peptide, has been shown to increase plasma luteinizing hormone (LH) through luteinizing hormone-releasing hormone (LHRH). This led us to investigate, using both light and electron microscopy, whether GALP-containing neurons in the rat brain make direct inputs to LHRH-containing neurons. As LHRH-containing neurons are very difficult to demonstrate immunohistochemically with LHRH antiserum without colchicine treatment, we used a transgenic rat in which LHRH tagged with enhanced green fluorescence protein facilitated the precise detection of LHRH-producing neuronal cell bodies and processes. This is the first study to report on synaptic inputs to LHRH-containing neurons at the ultrastructural level using this transgenic model. We also used immunohistochemistry to investigate the neuronal interaction between GALP- and LHRH-containing neurons. The experiments revealed that GALP-containing nerve terminals lie in close apposition with LHRH-containing cell bodies and processes in the medial preoptic area and the bed nucleus of the stria terminalis. At the ultrastructural level, the GALP-positive nerve terminals were found to make axo-somatic and axo-dendritic synaptic contacts with the EGFP-positive neurons in these areas. These results strongly suggest that GALP-containing neurons provide direct input to LHRH-containing neurons and that GALP plays a crucial role in the regulation of LH secretion via LHRH.     

The distribution of tyrosine hydroxylase immunoreactivity in the brains of male and female zebra finches

A system of brain nuclei controls song learning and behavior in zebra finches (Poephila guttata). The size of song-control nuclei are much larger in males, which sing, than in females, which do not sing. This study examined the distribution of fibers, terminals, and cell bodies that are immunoreactive for tyrosine hydroxylase (TH) (the rate-limiting enzyme in the synthesis of catecholamines) in song-control nuclei of adult males and females and juvenile males. In addition, the broad pattern of TH staining throughout the brain was described. There was a sex difference in TH immunoreactivity within song-control nuclei: males had light to moderate staining in all three cortical nuclei examined, whereas females had little or no label in corresponding areas [lateral magnocellular nucleus of the anterior neostriatum (IMAN), higher vocal center (HVC), and robust nucleus of the archistriatum (RA)]. The song-control nucleus area X (X), located in the striatum of avian basal ganglia, was more darkly stained than the surrounding striatum only in males; X was not defined by more intense immunoreactivity in females and hence could not be visualized. There were no apparent differences in TH staining in males ranging in age from 50 days to adulthood (>90 days). Outside of the song-control system there were no substantive differences as a function of sex or age in the pattern or intensity of TH labeling. Major areas of telencephalic staining included the striatal region of basal ganglia, which was covered with dense, fine-grained label, and the septum, where cell bodies were encircled by extremely well-labeled thick processes. In the diencephalon, the preoptic area and hypothalamus included a complex pattern of darkly stained somata and fiber and terminal labeling. Darkly stained somata surrounded the pretectal nucleus, and labeled processes ramified throughout the superficial layers of the optic tectum. The midbrain and hindbrain contained a dense plexus of extremely dark cell bodies corresponding to mammalian substantia nigra, adjacent tegmental areas, and locus ceruleus. Labeled hindbrain cells were also seen in the pontine region, around nucleus solitarius, and in the ventrolateral medulla. © 1993 John Wiley & Sons, Inc.     

Lateral septal projections onto tubero-infundibular neurons in the hypothalamus of the guinea pig

Efferent projections of the lateral septal nucleus (LS) to the preoptic area and the hypothalamus were identified in 20 female guinea pigs after iontophoretic injection of the anterograde axonal tracer Fluoro-Ruby. Tubero-infundibular (TI) neurons of the preoptic area and the hypothalamus were retrogradely labeled after intracardiac injection of Granular Blue or Fluoro-Gold. Magnocellular neurons of the supraoptic and paraventricular nuclei were also labeled. The double labeling procedure allowed an estimation of the extent of the direct relationship between LS efferents and TI neurons. Contacts between lateral septal fibers and TI cell bodies were mainly observed at the light-microscopical level in the preoptic area. A group of labeled fibers coursing along the third ventricle established sparse connections with hypothalamic periventricular TI neurons. A few appositions was observed in the infundibular (arcuate) nucleus, suggestive of a monosynaptic regulation of TI neurons by a septo-arcuate tract. Close association with labeled magnocellular neurons was also noted at the edge of the supraoptic and paraventricular nuclei. The sparse but direct connections between LS and TI neurons may be involved in the neuroendocrine functions of the LS.     

Studies on hypothalamo-pituitary corticoliberin system. I. Localization of corticotropin-releasing factor (CRF)- and neurophysin-immunoreactive neurons in the Mongolian gerbil (Meriones unguiculatus)

The immunohistochemical localization of CRF- and neurophysin-containing neurons in the hypothalamus of the Mongolian gerbil was studied by means of the PAP technique. The CRF-immunoreactive fibers were detected mainly in the outer layer of the median eminence of intact adult male gerbils. The CRF-positive neurons respond to aminoglutethimide (Elipten, Ciba) administration by showing increased immunoreactivity and an increase in the number of stained cell bodies in the parvocellular division of the paraventricular nucleus. Aminoglutethimide treatment results also in an increase in the number of neurophysin-immunoreactive nervous fibers localized in the internal layer of the median eminence. However, CRF-immunoreactive fibers are observed mainly in the outer layer of the median eminence while neurophysin-immunopositive axons are seen predominantly in the internal layer of this region. Since the axons of paraventricular neurons run to the median eminence and their staining ability is changed due to aminoglutethimide, their involvement in the endocrine control of hypophysial ACTH release is postulated.