Immunocytochemical localization of corticotropin-releasing factor in the brain of the turtle,Mauremys caspica

Brain sections of the turtle, Mauremys caspica were studied by means of an antiserum against rat corticotropin-releasing factor. Immunoreactive neurons were identified in telencephalic, diencephalic and mesencephalic areas such as the cortex, nucleus caudatus, nucleus accumbens, amygdala, subfornical organ, paraventricular nucleus, hypothalamic dorsolateral aggregation, nucleus of the paraventricular organ, infundibular nucleus, pretectal nucleus, periventricular grey, reticular formation and nucleus of the raphe. Many immunoreactive cells located near the ependyma were bipolar, having an apical dendrite that contacted the cerebrospinal fluid. Immunoreactive fibers were seen in these locations and in the lamina terminalis, lateral forebrain bundle, supraoptic nucleus, median eminence, neurohypophysis, tectum opticum, torus semicircularis and deep mesencephalic nucleus. Parvocellular bipolar immunoreactive neurons from the paraventricular and infundibular nuclei projected axons that joined the hypothalamo-hypophysial tract and reached the outer zone of median eminence, and the neural lobe of the hypophysis where immunoreactive fibers terminated close to intermediate lobe cells. From these results it can be concluded that, as in other vertebrates, corticotropin-releasing factor in the turtle may act as a releasing factor and, centrally, as a neurotransmitter or neuromodulator.     

针刺“足三里”穴下丘脑血管加压素(Vp)样细胞的形态学变化——免疫组织化学法

采用免疫组化PAP技术,在电针大鼠“足三里”穴位后,观察丘脑下部Vp样神经元的变化。发现视上核与室旁核Vp样大神经元数目增多、胞体胀大,并伸出细长突起。室旁核少数串珠状神经纤维可插入第三脑室壁的细胞之间。在视交叉上核腹内侧Vp小神经元密集,而背外侧反应阳性神经元较少。视上核与室旁核间的神经元岛的细胞体积增大、轴索变长伸向视上区。该区的串珠状纤维集合成束达正中隆起的外层。以上实验结果提示,电针“足三里”可促进下丘脑有关核团Vp样物质的合成与分泌。     

The serotoninergic system of the brain of the viper, Vipera aspis. An immunohistochemical study

Serotoninergic cell bodies and fibers in the brain of the viper, Vipera aspis, were visualized by immunohistochemistry. Immunoreactive cell bodies were observed in the diencephalic hypothalamic periventricular organ and in the dorsal wall of the infundibular recess, in the nuclei raphe superior and inferior of the midbrain and hindbrain, and to a lesser extent in the nuclei reticularis superior, reticularis inferior and reticularis lateralis. In contrast to other reptilian species, serotoninergic cells were also observed in the central gray matter of the midbrain in the neighbourhood of the nucleus of the trochlear nerve. Immunoreactive fibers are widely distributed throughout the brain of the viper. In the olfactory bulb, fibers were observed in the internal plexiform layer and mitral cell layer. The cerebral cortex contains the highest density of fibers in the dorsal region. The distribution of immunoreactive fibers in the dorsal ventricular ridge is extremely heterogeneous, and five subcomponents of this structure can be distinguished. The majority of diencephalic and mesencephalic structures that contain immunoreactive fibers are also primary visual centres: the nuclei geniculatus lateralis pars dorsalis, the n. posterodorsalis and n. opticus tegmenti, and the optic tectum. Serotoninergic fibers in the nuclei of the oculomotor and motor cranial nerves (III, IV, V, VII, X) are disposed in a tightly woven basket around the non-immunoreactive cell bodies of the motoneurons. These findings, together with the available literature, suggest that the serotoninergic system in snakes is comparable to that in lizards, with a massive ascending projection of fibers from the n. raphe superior to mesencephalic and prosencephalic structures, and a descending projection from the n. raphe inferior to the spinal cord.     

The distribution of vasotocin and mesotocin immunoreactivity in the brain of the snake,Bothrops jararaca

Polyclonal antibodies against vasotocin (AVT) and mesotocin (MST) were used to explore the distribution of these peptides in the brain of the snake Bothrops jararaca. Magnocellular AVT- and MST-immunoreactive (ir) perikarya were observed in the supraoptic nucleus (SON), being AVT-ir neurons more numerous. A portion of the SON, in the lateroventral margin of the diencephalon ventrally to optic tract, showed only AVT-ir perikarya and fibers. However, the caudal most portion displayed only mesotocinergic perikarya. Parvocellular and magnocellular AVT- and MST-ir perikarya were present in the paraventricular nucleus (PVN) being AVT-ir fibers more abundant than MST-ir. Vasotocinergic perikarya were also found in a dorsolateral aggregation (DLA) far from the PVN. Mesotocinergic perikarya were also present in the recessus infundibular nucleus and ependyma near to paraventricular organ. Nerve fibers emerging from supraoptic and paraventricular nuclei run along the diencephalic floor, internal zone of the median eminence (ME) to end in the neural lobe. Also a dense network of AVT- and MST-ir fibers was present in the external zone of the ME, close to the vessels of the hypophysial portal system. As a rule, all regions having vasotocinergic and mesotocinergic perikarya also showed immunoreactive fibers. Vasotocinergic and mesotocinergic fibers but not perikarya were found in the lamina terminalis (LT). Moreover AVT-ir fibers were present in the nucleus accumbens and MST-ir fibers in the septum. In mesencephalon and rhombencephalon MST-ir fibers were more numerous than AVT-ir fibers. Vasotocinergic and mesotocinergic fibers in extrahypothalamic areas suggest that these peptides could function as neurotransmitters and/or neuromodulators in the snake B. jararaca.     

Ontogeny of vasotocinergic and mesotocinergic systems in the brain of the South African clawed frog Xenopus laevis

For a better understanding of the development of neurotransmitter systems and of their putative functional significance during ontogenesis, the development of the vasotocin (AVT) and mesotocin (MST) systems in the brain of Xenopus laevis was studied by means of immunohistochemical techniques. Weakly immunoreactive fibers were already present at late embryonic stage 38 in the caudoventral part of the telencephalon and in the ventral part of the diencephalon. The earliest immunodetectable AVT and MST immunoreactive cell bodies were found in the developing preoptic area at late embryonic stage 43. At the end of the embryonic period (stage 45), AVT immunoreactive fibers have reached the future medial amygdala, the midbrain tegmentum, the median eminence and the neural lobe of the pituitary. When compared with AVT immunoreactive fibers, the development of MST fibers shows some temporal delay. During the premetamorphosis (stages 45–52), AVT immunoreactive cell bodies appear in the medial part of the suprachiasmatic nucleus, the dorsal infundibular region, and the midbrain tegmentum, whereas fibers can now be traced to the nucleus accumbens, the septum and the medial amygdala in the forebrain, to the midbrain tegmentum, the reticular formation, the raphe nuclei, and the solitary tract nucleus in the brainstem, and to the spinal cord. Further maturation of the AVT system during prometamorphosis (stages 53–58) includes the appearance of immunoreactive cell bodies in the lateral part of the suprachiasmatic nucleus, the ventral preoptic area, and the dorsal infundibular region. By the end of the metamorphosis (stage 65), the maturation of the AVT/MST systems reaches an almost adult-like pattern. It should be noted that in amphibians, in contrast to mammals, the early appearance of the AVT/MST systems, including their extensive extrahypothalamic component, suggests that the two neuropeptidergic systems may play a significant role during development.     

The effects of prenatal stress on the development of hypothalamic paraventricular neurons in fetal rats.

The present experiments focused on the influence of prenatal stress on the development of neurons of the hypothalamic paraventricular nucleus in the fetal rat, including corticotropin-releasing factor-containing neurons. Prenatal stress was administered by restraining pregnant rats in a small cage for either 30 (30-min stress group) or 240 min (240-min stress group) daily for three days from embryonic day 15 to 17, and the fetal brains were taken on embryonic day 18 for later analysis. Golgi-impregnated neurons of the paraventricular nucleus in the 240-min stress group revealed that the total length of the processes was significantly shorter than in the control (unstressed) and 30-min stress groups. In addition, the 240-min stress group showed an increase in the number of apoptotic cells in the fetal paraventricular nucleus. On the other hand, Golgi-impregnated neurons of the paraventricular nucleus in the 30-min stress group had a greater degree of cell differentiation as manifested by an increase in both the number of branch points and the total length of the processes from the cell body. Furthermore, the fetal paraventricular nucleus in the 30-min stress group showed enhanced corticotropin-releasing factor messenger RNA expression, while the varicosities of corticotropin-releasing factor-containing axons at the median eminence revealed more matured morphology such as shorter intervals between the varicosities. These findings suggest the duration-dependent effects of prenatal stress on the development of fetal hypothalamic paraventricular nucleus neurons, including corticotropin-releasing factor-containing neurons: long-lasting stress causes neurotoxic changes of fetal paraventricular nucleus neurons, whereas short-lasting stress facilitates the development of these fetal brain neurons. These morphological changes induced by prenatal stress may contribute to behavioral changes of the offspring after birth.     

Corticotropin-releasing factor innervation of the locus coeruleus region: distribution of fibers and sources of input.

Electrophysiologic studies support the hypothesis that corticotropin-releasing factor, the neurohormone that initiates adrenocorticotropin release during stress, also serves as a neurotransmitter in the pontine noradrenergic nucleus, the locus coeruleus. To elucidate the circuitry underlying proposed corticotropin-releasing factor neurotransmission in the locus coeruleus, the present study utilized immunohistochemical techniques to characterize corticotropin-releasing factor innervation of rat locus coeruleus and pericoerulear regions. Corticotropin-releasing factor-like immunoreactive fibers were identified in the locus coeruleus of colchicine- and non-colchicine-treated rats. However, corticotropin-releasing factor innervation of pericoerulear regions rostral and lateral to the locus coeruleus was more dense than that of the locus coeruleus proper. Double-labeling studies utilizing antisera directed against corticotropin-releasing factor and tyrosine hydroxylase indicated that corticotropin-releasing factor-like immunoreactive fibers overlap with tyrosine hydroxylase-like immunoreactive processes of locus coeruleus neurons, particularly in rostral medial and lateral regions. A group of corticotropin-releasing factor-like immunoreactive neurons was localized just lateral to the locus coeruleus and numerous corticotropin-releasing factor-like immunoreactive neurons were visualized just ventral to the rostral pole of the locus coeruleus in a region corresponding to Barrington's nucleus. None of these corticotropin-releasing factor-like immunoreactive neurons were tyrosine hydroxylase-positive. To determine the source of corticotropin-releasing factor-like immunoreactive fibers in the locus coeruleus, injections of the retrograde tracer [wheat germ agglutinin conjugated to inactivated (apo) horseradish peroxidase coupled to gold particles] were made into the locus coeruleus and sections were processed for corticotropin-releasing factor-like immunoreactivity.(ABSTRACT TRUNCATED AT 250 WORDS)     

The serotoninergic system of the brain of the viper, Vipera aspis. An immunohistochemical study

Serotoninergic cell bodies and fibers in the brain of the viper, Vipera aspis, were visualized by immuno-histochemistry. Immunoreactive cell bodies were observed in the diencephalic hypothalamic periventricular organ and in the dorsal wall of the infundibular recess, in the nuclei raphe superior and inferior of the midbrain and hindbrain, and to a lesser extent in the nuclei reticularis superior, reticularis inferior and reticularis lateralis. In contrast to other reptilian species, serotoninergic cells were also observed in the central gray matter of the midbrain in the neighbourhood of the nucleus of the trochlear nerve. Immunoreactive fibers are widely distributed throughout the brain of the viper. In the olfactory bulb. fibers were observed in the internal plexiform layer and mitral cell layer. The cerebral cortex contains the highest density of fibers in the dorsal region. The distribution of immunoreactive fibers in the dorsal ventricular ridge is extremely heterogeneous, and five subcomponents of this structure can be distinguished. The majority of diencephalic and mesencephalic structures that contain immunoreactive fibers are also primary visual centres: the nuclei geniculatus lateralis pars dorsalis, the n. posterodorsalis and n. opticus tegmenti, and the optic tectum. Serotoninergic fibers in the nuclei of the oculomotor and motor crainal nerves (III, IV, V, VII, X) are disposed in a tightly woven basket around the non-immunoreactive cell bodies of the motoneurons. These findings, together with the available literature, suggest that the serotoninergic system in snakes is comparable to that in lizards, with a massive ascending projection of fibers from the n. raphe superior to mesencephalic and prosencephalic structures, and a descending projection from the n. raphe inferior to the spinal cord.     

Immunocytochemical ultrastructural study of hypothalamic neurons containing corticotropin-releasing factor in normal and adrenalectomized rats

The neurons of the rat hypothalamus which secrete corticotropin-releasing factor were studied by using a pre-embedding immunocytochemical staining technique that improves both the penetration of immunoreagents within the tissue and the preservation of the ultrastructural morphology of labeled structures. Comparison was made between the subcellular location of corticotropin-releasing factor-41 in perikarya of the paraventricular nucleus and axons of the median eminence, both in intact and adrenalectomized animals either untreated or 24 h after the intracerebral injection of colchicine. Morphometric analysis of the numerical density and of the diameter of corticotropin-releasing factor immunoreactive neurosecretory granules in axons of the median eminence of rats not treated with colchicine, indicated that the main modifications induced by adrenalectomy concerned (1) the differential repartition of labeled granules within the preterminal and terminal axonal portions of the median eminence, and (2) the enlargement of the diameter of labeled granules contained in these axons (from 98 nm to 165 nm). In the hypothalamus of intact and adrenalectomized rats, colchicine treatment increased the number of corticotropin-releasing factor-immunoreactive granules in the neuronal perikarya and reduced their number in the axons, but both these variations were much more marked in adrenalectomized rats. Although the corticotropin-releasing factor immunoreactive granules that accumulated in the perikarya after colchicine treatment were slightly smaller than those in the corresponding axons, the diameter of perikaryal-labeled granules was larger in adrenalectomized than in intact animals (129 nm vs 93 nm). These findings fit the idea that adrenalectomy markedly stimulates both the synthesis and axonal excretion of secretory granules in the hypothalamic neurons secreting corticotropin-releasing factor. They also indicate that suppression of circulating corticosteroids induces qualitative modifications in these neurons leading to the visualization of larger neurosecretory granules, which may reflect differential synthesis and granular packing of synergistic peptides other than corticotropin-releasing factor and/or changes in the process of intragranular maturation of hormonal material.     

Immunocytochemical detection of corticotropin-releasing factor: multiple cross-reactions of a widely used carboxy-terminally directed corticotropin-releasing factor antiserum (code rC70) in rat hypothalamus

Forty-one-residue corticotropin-releasing factor is a physiologically significant mediator of the hypothalamic control of corticotropin secretion by the anterior pituitary gland. This releasing hormone is produced by parvicellular neurons in the hypothalamic paraventricular nucleus that project to the external zone of the median eminence. Recent immunocytochemical evidence based on work with a rabbit antiserum against rat corticotropin-releasing factor (code rC70) suggests that about half of the parvicellular corticotropin-releasing factor-containing neurons in the hypothalamic paraventricular nucleus synthesize vasopressin, another potent corticotropin secretagogue, while the rest of the cells do not. If this is indeed the case, the neurohumoral control of corticotropin release may be mediated via distinct hypothalamic effector pathways utilizing releasing hormone cocktails of varying composition. In the present study we have examined the specificity of various antisera against rat corticotropin-releasing factor in immunocytochemical staining. Male Wistar rats pretreated with colchicine were used throughout. The brain was fixed by perfusion with a Zamboni type fixative solution. Vibratome sections of the hypothalamus were immunostained with three different primary antisera (codes rC70, rCRF-3, oCRF-N) using the peroxidase-antiperoxidase or avidin-biotin complex methods. All three antisera stained cell groups previously described to be immunopositive for corticotropin-releasing factor. Most notably, however, rC70 labelled a significant number of additional cells, most readily identified in the arcuate and suprachiasmatic nuclei, as well as in the dorsolateral hypothalamic area caudal to the paraventricular nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neuropeptide Y: brain localization and central effects on plasma insulin levels in chicks

A rich network of NPY-like immunoreactive fibers was found in the paraventricular nucleus and the ventromedial region of the hypothalamus juxtapositioned to the third ventricle, including the median eminence. Brain regions, areas or nuclei found densely innervated by NPY-like immunoreactive fibers included the olfactory bulb region, septal area, organum vasculosum of the lamina terminalis, preoptic periventricular nucleus, hypothalamic periventricular nucleus, medial suprachiasmatic nucleus, subseptal (subfornical) organ, ventromedial hypothalamic nucleus, infundibular nucleus and nucleus tractus solitarius. NPY-like containing perikarya were localized within the hippocampus, bed nucleus of the stria terminalis and surrounding the nucleus rotundus and nucleus of the basal optic root. Since the immunocytochemical study showed that NPY was localized in brain structures known to alter food intake and the compound is a member of the pancreatic polypeptide family, a second study was designed to determine if the neuropeptide altered plasma concentrations of insulin, glucagon and glucose following intracerebroventricular administration. It was found that NPY significantly increased plasma concentration of insulin. It is proposed that two reasons why NPY is such a potent orexigenic agent is that the paraventricular nucleus and structures surrounding the third ventricle throughout the ventromedial hypothalamic region show high levels of NPY-like immunoreactivity. Secondly, NPY effects an increase in plasma insulin in the periphery.     

Atrial natriuretic factor-like immunoreactivity in the central nervous system of the frog

The distribution of atrial natriuretic factor-like immunoreactivity in the central nervous system of the frog Rana ridibunda was investigated by indirect immunofluorescence and the immunogold technique, using an antiserum generated in rabbits against synthetic atrial natriuretic factor (Arg 101-Tyr 126). A stereotaxic atlas of neurons containing atrial natriuretic factor-like material was prepared to show the widespread distribution of atrial natriuretic factor-positive cell bodies and fibres in the brain. Appreciable numbers of immunoreactive perikarya were observed in the dorsal and medial pallium, the medial septal nucleus, the anteroventral and ventrolateral areas of the thalamus, the lateral forebrain bundle, the posterocentral and posterolateral thalamic nuclei, the preoptic nucleus, the dorsal infundibular nucleus and the anteroventral tegmental nucleus of the mesencephalon. A heavy accumulation of atrial natriuretic factor-like immunoreactive cell bodies and very dense fibre bundles were noted in the interpeduncular nucleus of the mesencephalon. Fibres were generally seen where cell bodies were observed, particularly in all regions of the pallium and septum nuclei, in the ventral thalamus, the infundibular nucleus and the tegmental area. Moderate numbers of fibres were also noted in several regions where cell bodies were absent, mainly in the amygdala and the infundibular nucleus, the median eminence and most mesencephalic regions. At the electron microscopic level, the immunoreactivity was restricted to dense core vesicles and absent in clear vesicles. These results provide the first evidence for the presence of atrial natriuretic factor in the brain of a non-mammalian chordate. The localization of atrial natriuretic factor-positive material in the frog central nervous system suggests that this peptide may act as a neuromodulator or a neurotransmitter in amphibians.     

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.     

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.     

胎儿(36—40周)纹状体和下丘脑NPY免疫反应神经元的分布

本文用免疫细胞化学ABC法研究胎儿(36—40周)纹状体和下丘脑NPY免疫反应神经元的分布。在胎儿的纹状体发现尾状核和壳含有许多NPY免疫反应神经元的胞体和纤维。这两个区域的一些血管壁内也含有NPY免疫反应神经元的胞体和纤维。胎儿下丘脑的漏斗核和视上核含密集的NPY免疫神经元胞体,在室旁核偶尔也可见到少数免疫神经元胞体。本文首次报道了尾状核和壳的血管壁内及视上核含有NPY免疫反应神经元胞体。     

Immunohistochemical localization of chemokine CXCL14 in rat hypothalamic neurons

We immunohistochemically investigated the distribution of CXCL14, also called BRAK protein in the rat hypothalamus using anti-human CXCL14 serum. CXCL14-immunoreactive somata were localized in the periventricular area and paraventricular and supraoptic hypothalamic nuclei. In the former, immunoreactive neuronal somata, confirmed by double staining with a neuronal marker, NeuN, contained diffuse CXCL14-like immunoreactivity in their perikarya. In contrast, immunoreactive somata in the latter contained immunoreactive puncta within their perikarya. Very dense immunoreactive fibers and puncta were seen in the median eminence. Dense immunoreactive fibers were seen in the arcuate nucleus and ventromedial hypothalamic nucleus. Other hypothalamic areas contained a few immunoreactive fibers and puncta. These results demonstrated for the first time that CXCL14 protein is present in a subset of hypothalamic neurons and suggest that CXCL14 participates in hypothalamic functions such as control of autonomic nervous systems and/or participates in immune cell recruitment via the median eminence.     

Organization of ovine corticotropin-releasing factor immunoreactive neurons in the canine hypothalamo-pituitary system

The distribution of corticotropin-releasing factor immunoreactive (CRF-i) cell bodies and varicose fibers in the hypothalamus and the pituitary of the canine brain was studied by indirect immunofluorescence. CRF-i cell bodies were demonstrated mainly in the periventricular zone of the third ventricle, while some CRF-i cell bodies were scattered throughout the ventral part of the caudomedial hypothalamus. CRF-positive fibers were mostly situated in the median eminence. In addition some CRF-positive fibers were detected in the ventromedial aspect of the lateral hypothalamus forming a pathway arising from the CRF-i cell bodies, running via the median eminence through the infundibular stalk and terminating in the pars nervosa of the pituitary. The localization of the cell bodies and their projection points towards a possible (patho)physiological role of this peptide-transmitter system in the release of ACTH and beta-endorphin.     

Neurotransmitters,neuropeptides and binding sites in the rat mediobasal hypothalamus: effects of monosodium glutamate (MSG) lesions

Summary Indirect immunofluorescence histochemistry and receptor autoradiography were used to study the localization of transmitter-/peptidecontaining neurons and peptide binding sites in the mediobasal hypothalamus in normal rats and in rats treated neonatally with repeated doses of the neurotoxin monosodium-glutamate (MSG). In the arcuate nucleus, the results showed a virtually complete loss of cell bodies containing immunoreactivity for growth hormone-releasing factor (GRF), galanin (GAL), dynorphin (DYN), enkephalin (ENK), corticotropin-like intermediate peptide (CLIP), neuropeptide Y (NPY), and neuropeptide K (NPK). Tyrosine hydroxylase(TH)-, glutamic acid decarboxylase(GAD)-, neurotensin(NT)- and somatostatin(SOM)-immunoreactive (IR) cells were, however, always detected in the ventrally dislocated, dorsomedial division of the arcuate nucleus. In the median eminence, marked decreases in numbers of GAD-, NT-, GAL-, GRF-, DYN-and ENK-IR fibers were observed. The numbers of TH-, SOM-and NPY-IR fibers were in contrast not or only affected to a very small extent, as revealed with the immunofluorescence technique. Biochemical analysis showed a tendency for MSG to reduce dopamine levels in the median eminence of female rats, whereas no effect was observed in male rats. Autoradiographic studies showed high to moderate NT binding sites, including strong binding over presumably dorsomedial dopamine cells. In MSG-treated rats, there was a marked reduction in GAL binding in the ventromedial nucleus. The findings implicate that most neurons in the ventrolateral and ventromedial arcuate nucleus are sensitive to the toxic effects of MSG, whereas a subpopulation of cells in the dorsomedial division of the arcuate nucleus, including dopamine neurons, are not susceptible to MSG-neurotoxicity. The results indicate, moreover that the very dense TH-IR fiber network in the median eminence predominantly arises from the dorsomedial TH-IR arcuate cells, whereas the GAD-, NT-, GAL-, GRF-and DYN-IR fibers in the median eminence to a large extent arise from the ventrolateral arcuate nucleus. Some ENK-and NPK-positive cells in the arcuate nucleus seem to project to the lateral palisade zone of the median eminence, but most of the ENK-IR fibers in the median eminence, located in the medial palisade zone, seem to primarily originate from an area(s) located outside the arcuate nucleus, presumably the paraventricular nucleus. The NPY-positive fibers in the median eminence contain to a large extent immunoreactive dopamine -hydroxylase (DBH), and do not arise from the ventromedial arcuate nucleus. SOM-IR cells in the dorsal periventricular arcuate nucleus do not send major projections to the median eminence. The present findings thus show that MSG treatment represents a valuable tool to clarify the organization of chemically identified neuron populations in the arcuate nucleus-median eminence complex and provide further information for understanding the neuroendocrine effects of neonatal MSG treatment.