Immunohistochemical localization of avian pancreatic polypeptide-like immunoreactivity in the rat hypothalamus

The distribution of avian pancreatic polypeptide-like (APP) immunoreactivity within the rat hypothalamus was investigated with the indirect immunoperoxidase method. APP immunoreactive perikarya are found in largest numbers in the retrochiasmatic area, the arcuate nucleus, and the supracommissural portion of the interstitial nucleus of the stria terminalis. Small clusters of immunoreactive neurons are also consistently observed in the ventral aspect of the medial preoptic area and lateral hypothalamic area, immediately dorsolateral to the optic chiasm and tracts. These neurons are apparent in all animals but are more intensely strained and occur in larger numbers following colchicine pretreatment. Other immunoreactive neurons are visible only in colchine-treated rats and are scattered throughout the anterior and lateral hypothalamic areas and the supramammillary nucleus. Immunoreactive axons and terminal fields present an extensive and highly characteristic distribution throughout the hypothalamus, which in many instances exhibits differential distribution within specific subfields of hypothalamic nuclei and areas. The heaviest concentrations of APP immunoreactive axons are present in the periventricular nucleus throughout the rostrocaudal extent of the hypothalamus, the ventrolateral portion of the suprachiasmatic nucleus, the retrochiasmatic area, the parvocellular paraventricular nucleus, the ventral supraoptic nucleus, the perifornical nucleus, the ventral dorsomedial nucleus, and the arcuate nucleus. Moderate plexuses of immunoreactive fibers are also present in the medial preoptic area, the anterior and lateral hypothalamic areas, the nucleus circularis, the median eminence, and the ventral premammillary area. Other areas, such as the ventromedial nucleus, contain virtually no immunoreactive axons but are encapsulated by a dense plexus of immunoreactive terminals. The distribution of a major component of APP immunoreactive fibers exhibits a marked similarity to that of previously described norepinephrine-containing hypothalamic afferents. Other groups of APP immunoreactive perikarya and fibers appear to represent components of intrinsic diencephalic systems.     

Coexpression of dynorphin and neurokinin B immunoreactivity in the rat hypothalamus: Morphologic evidence of interrelated function within the arcuate nucleus

Considerable evidence suggests that dynorphin and neurokinin B (NKB) neurons in the hypothalamic arcuate nucleus participate in the sex-steroid regulation of reproduction. In the present study, we used dual-label immunofluorescence to explore the distribution of prodynorphin and proNKB immunoreactivity in the rat hypothalamus. Additionally, we investigated whether arcuate prodynorphin-ir (immunoreactive) neurons expressed the neurokinin 3 receptor (NK3R) or nuclear estrogen receptor-alpha (ERalpha). We found that the majority of prodynorphin-ir neurons in the rat arcuate nucleus expressed proNKB, whereas nearly all (99%) of the proNKB neurons were immunoreactive for prodynorphin. The arcuate nucleus was the only site in the hypothalamus where neuronal somata coexpressing prodynorphin and proNKB-immunoreactivity were identified. A dense plexus of double-labeled prodynorphin/proNKB-ir fibers was found within the arcuate nucleus extending to the median eminence and throughout the periventricular zone of the hypothalamus. Prodynorphin/proNKB fibers were also identified in the paraventricular nucleus, anterior hypothalamic area, medial preoptic area, median preoptic nucleus, anteroventral periventricular nucleus, and bed nucleus of the stria terminalis in a distribution consistent with previously described arcuate nucleus projections. Interestingly, the majority of prodynorphin-ir neurons in the arcuate nucleus expressed NK3R, and nearly 100% of the prodynorphin-ir neurons contained nuclear ERalpha. Our results suggest that there is a close functional relationship between dynorphin and NKB peptides within the arcuate nucleus of the rat, which may include an autofeedback loop mediated through NK3R. The diverse hypothalamic projections of fibers expressing both prodynorphin and proNKB provide evidence that these neurons may participate in a variety of homeostatic and neuroendocrine processes.     

Distribution of GAD-immunoreactive neurons in the diencephalon of the african lungfish Protopterus annectens: colocalization of GAD and NPY in the preoptic area

The distribution of GABAergic neurons was investigated in the diencephalon of the African lungfish, Protopterus annectens, by using specific antibodies directed against glutamic acid decarboxylase (GAD). A dense population of immunoreactive perikarya was observed in the periventricular preoptic nucleus, whereas the caudal hypothalamus and the dorsal thalamus contained only scattered positive cell bodies. Clusters of GAD-positive cells were found in the intermediate lobe of the pituitary. The diencephalon was richly innervated by GAD-immunoreactive fibers that were particularly abundant in the hypothalamus. In the periventricular nucleus, GAD-positive fibers exhibited a radial orientation, and a few neurons extended processes toward the third ventricle. More caudally, a dense bundle of GAD-immunoreactive fibers coursing along the ventral wall of the hypothalamus terminated into the median eminence and the neural lobe of the pituitary. Double-labeling immunocytochemistry revealed that GAD and neuropeptide tyrosine (NPY)-like immunoreactivity was colocalized in a subpopulation of perikarya in the periventricular preoptic nucleus. The proportion of neurons that coexpressed GAD and NPY was higher in the caudal region of the preoptic nucleus. The distribution of GAD-immunoreactive elements in the diencephalon and pituitary of the African lungfish indicates that GABA may act as a hypophysiotropic neurohormone in Dipnoans. The coexistence of GAD and NPY in a subset of neurons of the periventricular preoptic nucleus suggests that GABA and NPY may interact at the synaptic level.     

Mapping of neuropeptide Y-like immunoreactivity in the feline hypothalamus and hypophysis

The distribution of neuropeptide Y (NPY) in the cat hypothalamus and hypophysis was studied with the indirect immunofluorescence technique of Coons and co-workers (Coons, Leduc, and Connolly: J. Exp. Med. 102:49-60, 1955), which provided a detailed map of NPY-like immunoreactive neurons. The immunolabelling was detected in cell bodies, fibers, and terminallike structures widely distributed throughout the whole hypothalamus. A large population of medium-sized NPY-like immunoreactive cell bodies was localized in the area of arcuate nucleus. The number of immunoreactive cell bodies visualized was dramatically increased after intracerebroventricular injections of colchicine. Numerous immunolabelled cell bodies were also visible in the median eminence and scattered in the lateral hypothalamic area. Dense plexuses of NPY-immunoreactive fibers were observed in the arcuate nucleus, internal layer of median eminence, periventricular zone, and paraventricular nucleus. Other regions of hypothalamus displaying numerous NPY-like immunoreactive fibers included dorsal and ventrolateral hypothalamic areas. In contrast, certain hypothalamic areas were almost devoid of NPY-like immunoreactive fibers-namely, the mammillary bodies and suprachiasmatic nucleus. Finally, in neurohypophysis, bright immunofluorescent fibers were observed along the pituitary stalk and penetrating the neural lobe. These results suggest the widespread distribution of the NPY-containing neuronal systems in the cat hypothalamus and hypophysis.     

Light and electron microscopic immunocytochemistry of neurotensin-like immunoreactive neurons in the rat hypothalamus

Neurotensin-like immunoreactive neuronal perikarya, fibers and terminals in the rat hypothalamus, particularly in the arcuate nucleus, the paraventricular nucleus and the median eminence, were investigated by light and electron microscopic immunocytochemistry. The main distributional areas of immunoreactive neuronal perikarya were found to be the arcuate nucleus, the periventricular nucleus and the paraventricular nucleus by light microscopic immunocytochemistry. Immunoreactive neuronal perikarya showed a characteristic distributional pattern in the arcuate nucleus. In the paraventricular nucleus they were distributed in both the magnocellular and parvocellular portions. A large number of immunoreactive terminals were observed throughout the external layer of the median eminence, particularly its lateral portion. A moderate number of immunoreactive terminals were also observed in the internal layer of the median eminence. By electron microscopic immunocytochemistry immunoreactive neuronal perikarya both in the arcuate and paraventricular nuclei showed generally well-developed cell organelles such as mitochondria, r-ER, and Golgi complex. In addition, immunoreactive dense granules were dispersed throughout the perikarya. A large number of immunoreactive terminals containing immunoreactive dense granules, clear vesicles and mitochondria were observed in the vicinity of pericapillary spaces of the external layer of the median eminence. This observation strongly suggests that neurotensin-like immunoreactive substance is released into the portal capillaries.     

Distribution of somatostatin in the mouse brain: Effects of neonatal MSG treatment

Immunocytochemical analysis using antisera generated against the brain peptide somatostatin (SRIF) was examined in the brain of normal mice and in mice with chemical lesions of the arcuate nucleus produced neonatally by the administration of monosodium glutamate (MSG). In the normal mouse brain, SRIF immunoreactivity was seen in perikarya of the preoptic and hypothalamic periventricular nuclei. The normal distribution of SRIF fibers was apparent in several hypothalamic nuclei including the arcuate nucleus and in the internal and external zones of the median eminence. Extrahypothalamic sites of SRIF immunoreactive neurons and fibers were also observed throughout the telencephalon.At 60 days of age, certain neuroendocrine deficiencies, including growth parameters and obesity, were apparent in MSG-treated newborn mice. Analysis of SRIF projections in the brain of MSG-treated mice demonstrated a neurotoxic effect on arcuate neurons and a loss of SRIF projections to this region as well. Other components of the SRIF system in brain appeared unaffected. SRIF fibers of the arcuate region seem to originate from neuronal perikarya of the periventricular nucleus suggesting that MSG-induced endocrine deficiencies may be due to SRIF interactions at the level of the arcuate nucleus.     

Immunohistochemical studies of intrahypothalamic somatostatin-containing neurons in rat

Intrahypothalamic somatostatin-containing neurons were investigated immunohistochemically. In intact rats, immunoreactive cell bodies appeared in the rostral periventricular area, and immunoreactive beaded fibers were observed to terminate in the median eminence and to form delicate networks surrounding immunonegative cell bodies within the medial preoptic, suprachiasmatic, arcuate, ventromedial and premammillary nuclei. Intraventricular colchicine infusion resulted in the appearance of immunoreactive cell bodies in the arcuate, ventromedial and suprachiasmatic nuclei, and an increase in the number of cell bodies seen in the periventricular area. Complete deafferentation of the medial-basal hypothalamus excluding the rostral periventricular area caused the immunoreactive structures in the median eminence to disappear and enhanced the staining of periventricular cell bodies. In the arcuate and ventromedial nuclei, the immunoreactive fiber networks were left intact and the immunoreactive cell bodies were occasionally recognized. Horizontal knife cut between the arcuate nuclei and median eminence did not alter immunoreactivity in either region. Neonatal administration of MSG caused only the disappearance of arcuate nuclei. The results indicate that two kinds of somatostatin neuronal systems exist in rat hypothalamus: one is involved in the production of hormonal somatostatin and the other serves for the regulation of neuronal activities in restricted hypothalamic nuclei.     

Substance P-like immunoreactive neurons in the arcuate nucleus project to the median eminence in rat

Substance P-containing nerve fibers in the median eminence of rat arise in cells located in the arcuate nucleus. Two days following surgical lesioning of the median eminence immunoreactive substance P accumulated in neuronal perikarya in the middle part (rostrocaudally) of the arcuate nucleus, mainly in its ventromedial portion. Substance P-immunostained cells appeared nowhere else in the hypothalamus following surgical lesion of the median eminence while they were found in several hypothalamic and extrahypothalamic cell groups after colchicine treatment.     

Distribution of cholecystokinin-like-immunoreactive neurons in the guinea pig forebrain

The distribution of cholecystokinin (CCK)-immunoreactive nerve fibers and cell bodies was studied in the forebrain of control and colchicine-treated guinea pigs by using an antiserum directed against the carboxyterminus of CCK octapeptide (CCK-8) in the indirect immunoperoxidase technique. Virtually all forebrain areas examined contained immunoreactive nerve fibers. A dense innervation was visualized in; neocortical layers II-III, piriform cortex, the medial amygdala, the medial preoptic area, a circumventricular organ-like structure located at the top of the third ventricle in the preoptic area, the subfornical organ, the posterior bed nucleus of the stria terminalis, the posterior globus pallidus (containing labeled woolly fiber-like profiles), the ventromedial hypothalamus, the median eminence, and the premammillary nucleus. A moderately dense innervation was visualized elsewhere excepted in the septum and thalamus where labeled axons were comparatively few. Immunoreactive perikarya were abundant in: neocortex (especially layers II-III), piriform cortex, amygdala, the median preoptic nucleus, the bed nucleus of the stria terminalis, the hypothalamic paraventricular (parvicellular part), arcuate, and dorsomedial (pars compacta) nuclei, the dorsal and perifornical hypothalamic areas, and throughout the thalamus. Areas also containing a moderate number of labeled cell bodies were the medial preoptic area, the globus pallidus, the caudate-putamen, and the periventromedial area in the hypothalamus. Immunostained perikarya were absent or only occasionally observed in the septum, the suprachiasmatic nucleus, the magnocellular hypothalamoneurohypophyseal nuclei, and the ventral mesencephalon. In the adenohypophysis, corticomelanotrophs were labeled in both males and females, and thyrotrophs were labeled in females only. This distribution pattern of CCK-8 immunoreactivity is compared to those previously recorded in other mammals. This shows that very few features are peculiar to the the guinea pig. It is discussed whether some interspecific differences in immunostaining are real rather than methodological.     

GRF immunoreactive neurons in the paraventricular nucleus of the rat: an immunohistochemical study with monoclonal and polyclonal antibodies

Our study demonstrates a complex GRF neuronal system within the rat hypothalamus. Using both high affinity polyclonal and high specificity monoclonal antibodies to rat (r) GRF, we have substantiated evidence for immunoreactive GRF (GRF-i) perikarya in the parvocellular portion of the paraventricular nucleus. Other hypothalamic areas containing rGRF-positive perikarya include the lateral arcuate nucleus, lateral hypothalamus, perifornical area and dorsomedial nucleus. GRF-i neuronal terminals were seen in the external zone of the median eminence, more rostrally in the periventricular nucleus, and near the suprachiasmatic nucleus and more caudally in the dorsomedial nucleus and ventral premammillary nucleus.     

Somatostatin neurons and their projections in dog diencephalon.

Immunocytochemical localization of the tetradecapeptide somatostatin was performed in dog brain using the unlabeled antibody enzyme method. A large population of immunoreactive neurons was seen in the periventricular areas of the preoptic area and anterior hypothalamus. This field of neurons extended into the paraventricular nucleus, arcuate nucleus and tuberal areas surrounding the ventromedial nuclei. Fibers from the periventricular somatostatin cells projected into the median eminence, the third ventricle, the pars nervosa of the hypophysis, the organum vasculosum of the lamina terminalis, the medial preoptic area and the interstitial nucleus of the stria terminalis. The tuberal cells projected to the ventromedial nucleus and the cells of the arcuate nucleus terminated within the arcuate nucleus as well as within the contact zone of the median eminence. These findings suggest that somatostatin can exert hormonal effects via the vasculature or the cerebrospinal fluid, or transmitter and/or neuromodulatory effects via contacts with other neurons.     

The hypothalamic ‘tuberoinfundibular’ system of the rat as demonstrated by horseradish peroxidase (HRP) microiontophoresis

Microiontophoresis of horseradish peroxidase (20%) into the median eminence of the rat has allowed visualization of perikarya and axon projections of the tuberoinfundubular system after retrograde transport. Cells projecting to the median eminence were found in the periventricular regions of the hypothalamus and were particularly pronounced in dorsal portions of the rostral arcuate nucleus, the medial division of the paraventricular nucleus, and within the anterior periventricular nucleus. Labeling of perikarya within the ventromedial nucleus was rarely found. No labeling by HRP was found within cells of the dorsomedial, anterior, suprachiasmatic, preoptic, lateral hypothalamic nuclei or within the septal and amygdaloid nuclei. Axons from identifiable cells were located within the periventricular neuropil and contained within the baso-lateral portions of the hypothalamic-hypophysial tract.     

Immunocytochemical distribution of [Met]enkephalin-Arg-Gly-Leu immunoreactivity in the rat diencephalon

Recently, [Met]Enkephalin-Arg-Gly-Leu (MEAGL) was isolated from bovine adrenal glands, and it was found to be derived exclusively from proenkephalin. Therefore, we investigated the distribution of MEAGL-like immunoreactive neuronal perikarya and fibers in the rat diencephalon pretreated with colchicine by PAP immunocytochemistry. In the thalamus MEAGL immunoreactive neuronal perikarya were distributed in the paraventricular nucleus and the ventral part of the lateral geniculate nucleus. Immunoreactive fibers were found in the paraventricular, paracentral, anteroventral, reuniens and rhomboid nuclei. In addition, immunoreactive fibers were also noted in the anterior pretectal nucleus. In the hypothalamus, immunoreactive neuronal perikarya were observed in the medial preoptic area, anterior and lateral hypothalamic nuclei, perifornical region, parvocellular and postero-magnocellular regions of paraventricular nucleus, ventromedial nucleus, dorsomedial nucleus, arcuate nucleus, premammillary, medial mammillary and lateral mammillary nuclei. The distribution of immunoreactive fibers was similar to that of neuronal perikarya. However, immunoreactive fibers were also observed in the supraoptic and suprachiasmatic nuclei where no immunoreactive neuronal perikarya were detected. Numerous immunoreactive fibers were detected in the external layer of the median eminence, but there were few in the internal layer. The similarity and difference in the distribution between MEAGL and other proenkephalin peptides such as [Met]enkephalin were also discussed.     

Seasonal changes in methionine-enkephalin immunoreactivity in the brain of a hibernator, Spermophilus columbianus

To identify the actual location of central endogenous opioid systems which may be involved in regulating the hibernation cycle, differences in the pattern of central methionine-enkephalin (Met-EK) immunoreactivity were compared between hibernating (body temperature, Tb = 7 degrees C) and non-hibernating (Tb = 37 degrees C) Columbian ground squirrels using the peroxidase-antiperoxidase technique. In non-hibernating animals, Met-EK-immunoreactive perikarya were observed in telencephalic (putamen, caudate nucleus, medial septum-diagonal band complex, amygdala) and diencephalic (periventricular hypothalamic nucleus, lateral hypothalamic area) regions, whereas immunoreactive fibers were found in the lateral septum, stria terminalis nucleus, various hypothalamic areas, arcuate nucleus, median eminence, thalamic intralaminar, periventricular nucleus and lateral habenular nucleus. Compared to the non-hibernating animal, a marked increase in the number of Met-EK-immunoreactive fibers was found in the lateral septal nucleus, the periventricular nucleus, the intralaminar thalamus and the paraventricular hypothalamus of hibernating ground squirrels. Since these changes in immunoreactivity were not observed in the artificially induced hypothermic ground squirrels (Tb = 7 degrees C), it is unlikely that the dissimilarity in immunoreactivity between animals from different hibernating phases is due to differences in their Tb. In combination with our previous studies, these results tend to suggest that hibernation may be brought about by an increase in endogenous opioid activity, especially in the lateral septal region.     

Biochemical mapping of somatostatinergic systems in rat brain: Effects of periventricular hypothalamic and medial basal amygdaloid lesions on somatostatin-like immunoreactivity in discrete brain nuclei

Immunohistochemical studies have demonstrated the presence of somatostatin (growth hormone release-inhibiting factor)-positive cell bodies in the periventricular nucleus of the hypothalamus and in the medial-basal amygdala. In order to map biochemically the projections of these cell groups, electrolytic lesions were made in these structures and somatostatin was measured by radioimmunoassay in microdissected brain nuclei. Bilateral destruction of the periventricular nucleus significantly decreased somatostatin-like immunoreactivity (SLI) in the median eminence, and in the rostral periventricular, medial preoptic and arcuate nuclei. Bilateral lesions placed in the medial-basal amygdala significantly decreased SLI in the median eminence and suprachiasmatic nucleus. Similar depletions were observed following lesions of the stria terminalis. These results suggest that both the periventricular and amygdaloid somatostatin systems may participate in the regulation of growth hormone secretion via their projections to the median eminence and other hypothalamic nuclei.     

Distribution of corticotropin-releasing hormone immunoreactivity in golden hamster brain.

The distribution of corticotropin-releasing hormone-immunoreactive (CRH-IR) neurons and fibers was observed in golden hamsters. CRH-IR neurons and fibers were observed within the hypothalamus, thalamus, amygdala, cortex, midbrain, and hindbrain. The largest numbers of CRH-IR neurons were seen within the magno- and parvocellular divisions of the paraventricular nucleus of the hypothalamus and within the septum, bed nucleus of the stria terminalis, preoptic area continuum. The highest density of immunoreactive fibers was observed in the external zone of the median eminence. In addition, many immunoreactive fibers were observed within the bed nucleus of the stria terminalis and the preoptic area. The distribution obtained in hamsters was compared with previously reported distributions from rats, and both were generally similar.     

Melanin-concentrating hormone-producing neurons in birds.

The peptidergic melanin-concentrating hormone (MCH) system was investigated by immunocytochemistry in several birds. MCH perikarya were found in the periventricular hypothalamic nucleus near the paraventricular organ and in the lateral hypothalamic areas. Immunoreactive fibers were very abundant in the ventral pallidum, in the nucleus of the stria terminalis, and in the septum/diagonal band complex, where immunoreactive pericellular nets were prominent. Many fibers innervated the whole preoptic area, the lateral hypothalamic area, and the infundibular region. Some fibers also reached the dorsal thalamus and the epithalamus. The median eminence contained only sparse projections, and the posterior pituitary was not labeled. Thus, in birds, a neurohormonal role for MCH is not likely. Immunoreactive fibers were observed in other regions, such as the intercollicular nucleus, stratum griseum periventriculare (mesencephalic tectum), central gray, nigral complex (especially the ventral tegmental area), reticular areas, and raphe nuclei. Although no physiological investigation concerning the role of MCH has been performed in birds, the distribution patterns of the immunoreactive perikarya and fibers observed suggest that MCH may be involved in functions similar to those described in rats. In particular, the projections to parts of the limbic system (ventropallidal ganglia, septal complex, hypothalamus, dorsal thalamus, and epithalamus) and to structures concerned with visceral and other sensory information integration suggest that MCH acts as a neuromodulator involved in a wide variety of physiological and behavioral adaptations (arousal) with regard to feeding, drinking, and reproduction.     

Neurotensin in the rat median eminence: the possible sources of neurotensin-like fibers and varicosities in the external layer

The possible sources of neurotensin-like immunoreactive axons in the median eminence were studied after several experimental surgical approaches including unilateral lateral retrochiasmatic area transection, midsagittal knife cut through the median eminence, complete surgical isolation of the medial basal hypothalamus and bilateral paraventricular nucleus lesions. Both immunohistochemical and radioimmunoassay data demonstrate that neurotensin-containing neuronal located in the hypothalamic arcuate nuclei represent the main source of neurotensin occurring in the external zone of the median eminence of the rat: (1) neither the complete isolation of the medial basal hypothalamus nor the transection of the major neuronal input channel to the median eminence in the lateral retrochiasmatic area altered neurotensin-like immunoreactivity in the median eminence; (2) bilateral lesioning of the paraventricular nucleus resulted in insignificant changes of neurotensin level in the median eminence; and (3) two days after lesioning the median eminence an increased amount of retrogradely accumulated neurotensin-like immunoreactivity was found in several perikarya of the arcuate nuclei due to the blockage of axonal transport in the transected fibers. Retrograde accumulation of neurotensin-like material in other cells scattered in the anterior hypothalamus (in the paraventricular, paraventricular and anterior hypothalamic nuclei) indicates that in addition to the arcuate neurons these neurons may also participate in the neurotensin innervation of the median eminence.     

The distribution of growth-hormone-releasing factor (GRF) immunoreactivity in the central nervous system of the rat: an immunohistochemical study using antisera directed against rat hypothalamic GRF

Immunohistochemical methods have been used to chart the distribution of rat hypothalamic growth-hormone-releasing factor (rhGRF) immunoreactivity in the brains of normal and colchicine-treated adult albino rats. The results suggest the existence of at least two distinct rhGRF-containing systems: one responsible for delivery of the peptide to portal vessels in the median eminence, and one whose relationship, if any, to hypophysiotropic function is less direct. A dense plexus of rhGRF-stained fibers was found throughout the external lamina of the median eminence that is the route by which the peptide is delivered to the anterior pituitary. This projection appears to arise primarily from a group of rhGRF-immunoreactive neurons centered in the arcuate nucleus. Some 1,000-1,500 rhGRF-positive neurons were counted on each side of the brain in rats pretreated with colchicine. Colocalization studies, using a sequential double staining technique, indicated that a subset of rhGRF-immunoreactive neurons in the arcuate region contain neurotensin immunoreactivity. No evidence was obtained for colocalization of rhGRF with either of two pro-opiomelanocortin-derived peptides (alpha-melanocyte-stimulating hormone, adrenocorticotropic hormone (1-24)) in individual neurons in the arcuate nucleus. Much smaller groups of neurons were localized in the parvicellular division of the paraventricular nucleus of the hypothalamus and in the dorsomedial nucleus, and it is unclear whether they contribute to the plexus of rhGRF-stained fibers in the median eminence. The only other region in the rat brain in which rhGRF-stained cells were found reliably was in the area that roughly encapsulates the caudal aspect of the ventromedial nucleus of the hypothalamus. Because cells in this region are not known to project to the median eminence, they may be assumed to contribute to the extrahypophysiotropic rhGRF-stained projections outlined below. From the level of the arcuate and ventromedial nuclei, rhGRF-immunoreactive fibers could be traced along the base of the brain and through the periventricular system to discrete terminal fields limited almost exclusively to the hypothalamus and adjoining parts of the basal telencephalon. All parts of the periventricular region of the hypothalamus receive an input, including the preoptic and anterior parts in which somatostatin-containing neurons that project to the median eminence are clustered. Other prominent terminal fields were localized in discrete parts of the dorsomedial, paraventricular, suprachiasmatic, and premammillary nuclei, and in the medial preoptic and lateral hypothalamic areas.(ABSTRACT TRUNCATED AT 400 WORDS)     

Distribution of galanin-like immunoreactivity in the brain of Rana esculenta and Xenopus laevis.

The immunocytochemical distribution of galanin-containing perikarya and nerve terminals in the brain of Rana esculenta and Xenopus laevis was determined with antisera directed toward either porcine or rat galanin. The pattern of galanin-like immunoreactivity appeared to be identical with antisera directed toward either target antigen. The distribution of galanin-like immunoreactivity was similar in Rana esculenta and Xenopus laevis except for the absence of a distinct laminar distribution of immunoreactivity in the optic tectum of Xenopus laevis. Galanin-containing perikarya were located in all major subdivisions of the brain except the metencephalon. In the telencephalon, immunoreactive perikarya were detected in the pars medialis of the amygdala and the preoptic area. In the diencephalon, immunoreactive perikarya were detected in the caudal half of the suprachiasmatic nucleus, the nucleus of the periventricular organ, the ventral hypothalamus, and the median eminence. In the mesencephalon, immunoreactive perikarya were detected near the midline of the rostroventral tegmentum, in the torus semicircularis and, occasionally, in lamina A and layer 6 of the optic tectum. In the myelencephalon, labelled perikarya were detected only in the caudal half of the nucleus of the solitary tract. Immunoreactive nerve fibers of varying density were observed in all subdivisions of the brain with the densest accumulations of fibers occurring in the pars lateralis of the amygdala and the preoptic area. Dense accumulations of nerve fibers were also found in the lateral septum, the medial forebrain bundle, the periventricular region of the diencephalon, the ventral hypothalamus, the median eminence, the mesencephalic central gray, the laminar nucleus of the torus semicircularis, several laminae of the optic tectum, the interpeduncular nucleus, the isthmic nucleus, the central gray of the rhombencephalon, and the dorsolateral caudal medulla. The extensive system of galanin-containing perikarya and nerve fibers in the brain of representatives of two families of anurans showed many similarities to the distribution of galanin-containing perikarya and nerve fibers previously described for the mammalian brain.