Immunohistochemical demonstration of serotonin-containing nerve fibers in the hypothalamus of the monkey,Macaca fuscata

Summary The distributional pattern of serotonin-containing nerve fibers in the hypothalamus of the monkey (Macaca fuscata) was analyzed with the use of the peroxidaseantiperoxidase method in conjunction with a highly sensitive and specific anti-serotonin serum. The highest concentrations of serotonin-immunoreactive varicose fibers were found in the nucleus praeopticus medialis, nucleus ventromedialis hypothalami, and the complex of mammillary nuclei (nucleus praemamillaris, supramamillaris, mamillaris medialis et lateralis). However, the nucleus suprachiasmaticus, where numerous serotoninergic fibers have been reported to occur in the rat, appeared to be almost devoid of these fibers. The infundibular stalk, and the intermediate and posterior lobes of the pituitary contained considerable numbers of immunoreactive fibers. The present study provides a morphological basis for possible clarification of the influence of serotoninergic projections on various neuroendocrine mechanisms in primates. Furthermore, an attempt was made to clarify the differences and similarities concerning the distributional patterns of serotoninergic nerve fibers within the monkey hypothalamus in contrast to the rat hypothalamus.Supported by grants (No. 56440022, 57214028) from the Ministry of Education, Science and Culture, Japan     

The hypothalamic neurosecretory system of the marine teleost fish, Mugil auratus risso.

The hypothalamic neurosecretory system of the marinefish, Mugil auratus, consists of two nuclei, viz., the nucleus praeopticus and the nucleus laterlis tuberis. Both are paired, and while those of the nucleus praeopticus are vertically arranged as L-shaped bodies, their strand-like counterparts in the nucleus lateralis tuberis extend in an antero-posterior direction. The two constituent bodies of the nucleus praeopticus lie on both sides of the third cerebral ventricle. Each is differentiated into a dorsal pars magnocellularis and a ventral pars parvocellularis. A nervous tract, the hypothalamo-hypophysial tract, extends posteriorly from each body, but it is not until after they penetrate the pituitary gland that they fuse into one structure, the neurohypophysis. Many neurosecretory granules accumulate in the neurohypophysis adjacent to the meta-adenohypophysial region, and fewer scattered granules of varying sizes are also present along the hypothalamo-hypophysial tracts. Inner to these hypothalamo-hypophysial tracts extend the two bodies of the nucleus lateralis tuberis along the infundibular region. Axons from this nucleus extend sideways, and as they merge with those adjacently disposed of the hypothalamo-hypophysial tracts, they enter the pituitary gland as a unified structure.     

Primary olfactory projections and the nervus terminalis in the African lungfish: implications for the phylogeny of cranial nerves

Primary olfactory and central projections of the nervus terminalis were investigated by injections of horseradish peroxidase into the olfactory epithelium in the African lungfish. In addition, gonadotropin-releasing hormone (GnRH) immunoreactivity of the nervus terminalis system was investigated. The primary olfactory projections are restricted to the olfactory bulb located at the rostral pole of the telencephalon; they do not extend into caudal parts of the telencephalon. A vomeronasal nerve and an accessory olfactory bulb could not be identified. The nervus terminalis courses through the dorsomedial telencephalon. Major targets include the nucleus of the anterior commissure and the nucleus praeopticus pars superior. some fibers cross to the contralateral side. A few fibers reach the diencephalon and mesencephalon. No label is present in the "posterior root of the nervus terminalis" (= "Pinkus's nerve" or "nervus praeopticus"). GnRH immunoreactivity is lacking in the "anterior root of the nervus terminalis," whereas it is abundant in nervus praeopticus (Pinkus's nerve). These findings may suggest that the nervus terminalis system originally consisted of two distinct cranial nerves, which have fused-in evolution-in most vertebrates. Theories of cranial nerve phylogeny are discussed in the light of the assumed "binerval origin" of the nervus terminalis system.     

Somatostatin in the brain and the pituitary of some teleosts

Summary Immunocytochemical investigations show that somatostatin (SRIF)-like immunoreactive material is present in the brain and the pituitary of nine different species of teleosts. In the brain, immunoreactive perikarya and fibers are observed in the preoptic periventricular nucleus, the entopeduncular nucleus, the anterior periventricular nucleus, and the nucleus lateralis tuberis. In the pituitary, SRIF-like-immunoreactive fibers occur in the proximal pars distalis (PPD), which contains the growth hormone (GH)-secreting cells. Nerve fibers are scattered among GH cells (cyprinids), or end on the basal lamina at the neuroglandular interface of the PPD (eel, salmonids). In the eel, the proximal neurohypophysis does not penetrate deeply into the PPD that is very poorly vascularized. In some species, e.g. Myoxocephalus, SRIF-like immunoreactive fibers are also observed in the caudal neurohypophysis, and even among MSH cells of the pars intermedia.In long-term starved carps and eels, the amount of SRIF-like material in the pituitary is clearly reduced. A possible role of SRIF in the concomitant stimulation of GH cells is discussed.     

Immunohistochemical localization of corticotropin-releasing factor (CRF)-containing neurons in the hypothalamus of the Japanese quail,Coturnix coturnix

Immunohistochemical localization of corticotropin-releasing factor (CRF)-like immunoreactivity in the brain of the Japanese quail was studied by means of the peroxidase anti-peroxidase (PAP) method. CRF-immunopositive perikarya of parvocellular neurons were observed mainly in the nucleus praeopticus medialis and nucleus paraventricularis. Additional perikarya were also detected in the nucleus hypothalamicus posterior medialis in the hypothalamus and in the non-hypothalamic nucleus accumbens, nucleus septalis lateralis and nucleus dorsomedialis and dorsolateralis thalami. No CRF immunoreaction was found to coexist with the vasotocin (Vt)-containing system in comparative examination of consecutive sections treated with anti-vasopressin (Vp) serum. The CRF-immunoreactive fibers were detected mainly in the external layer of the anterior median eminence but not in its posterior division. Unilateral adrenalectomy induced the marked reduction in number of the CRF immunopositive fibers in the anterior median eminence.     

Immunocytochemical demonstration of growth hormone,prolactin and somatostatin-like immunoreactivities in the brain of larval,young adult and upstream migrant adult sea lamprey,Petromyzon marinus

Summary Growth hormone, prolactin and somatostatinlike immunoreactivities were demonstrated in the brains of larval, young adult (parasitic) and upstream migrant adult sea lampreys, Petromyzon marinus, by means of immunoperoxidase techniques. Growth hormone (GH) and prolactin (PRL) were observed within separate perikarya in the nucleus praeopticus, within fibers in the commissura praeinfundibularis, and in nerve endings within the neurohypophysis of larval and adult-stage lampreys. Cell bodies demonstrating immunoreactive growth hormone were more numerous than those reactive for prolactin. Unlike in the upstream migrant adult lamprey, no GH or PRL was demonstrated in the adenohypophysis of larval or parasitic lamprey.Somatostatin (SRIF)-like immunoreactive neurons were demonstrated in the nucleus commissurae praeinfundibularis, anterior and posterior pars ventralis hypothalami, pars dorsalis thalami, and the tegmentum motorium rhombencephali of larval, parasitic and upstream migrant adult lampreys. Many of the SRIF containing neurons within the hypothalamus were cerebrospinal fluid (CSF)-contacting cells. SRIF fibers were found throughout most of the brain predominating within the nucleus praeopticus, pars ventralis hypothalami, and the nucleus interpeduncularis. No SRIF immunoreactivity was found within the neurophyophysis. The possible functions of these peptides within the brain of the lamprey are discussed.     

Ontogeny of centers containing luteinizing hormone-releasing hormone in the brain of platyfish (Xiphophorus maculatus) as determined by immunocytochemistry

We have traced the development from birth to puberty of the ir-LHRH producing centers, the nucleus olfactoretinalis (NOR), nucleus praeopticus periventricularis (NPP) and nucleus lateralis tuberis pars posterior (NLT), in male sibling platyfish genetically determined by differing P alleles to mature at two different ages. In sexually immature fish of both genotypes ir-LHRH is first localized in the NOR in perikarya and neuronal fibers and in the NPP where it is limited to the fibers. At the onset of puberty in early maturing fish (11 weeks), ir-LHRH accumulates in perikarya and fibers of the NPP and NLT. Late maturing siblings first have ir-perikarya in the NPP and a few ir-fibers in the NLT at the same developmental stage but at a later age (25-26 weeks). Ir-perikarya are still not seen in the NLT in late-maturing fish even when maturation is complete. This pattern of a sequential development of the three ir-LHRH containing areas of the brain, which we refer to as a "cascade effect", is similar in early and late genotypes. It is directly correlated to stage of development and not to chronological age. It is clear that the appearance of LHRH producing brain centers precedes, and is presumably essential for, the completion of the development of pituitary gonadotrops and the subsequent maturation of the gonads. The functional significance of the NOR in puberty and reproduction and as a possible site of action for the P gene is discussed.     

Organization of tyrosine hydroxylase-immunoreactive neurons in the di-and mesencephalon of the American bullfrog (Rana catesbeiana) during metamorphosis

Summary We examined the immunocytochemical distribution of tyrosine hydroxylase, the rate-limiting enzyme in catecholamine synthesis, in the di-and mesencephalon of developing bullfrog tadpoles. Special attention was given to catecholaminergic innervation of the median eminence and pituitary. In premetamorphic tadpoles, tyrosine hydroxylase-immunoreactive neurons were visualized in the suprachiasmatic and infundibular hypothalamus, the ventral thalamus, and midbrain tegmentum by Taylor-Kollros stage V. The number of labeled neurons in all these areas increased as metamorphosis progressed. By mid-prometamorphosis, labeled neurons appeared in the preoptic recess organ as well as in the posterior thalamic nucleus. The majority of cells in the preoptic recess organ, as well as occasional neurons in the suprachiasmatic nucleus, exhibited labeled processes which projected through the ependymal lining of the preoptic recess to contact cerebrospinal fluid. The modified CSF-contacting neurons of the nucleus of the periventricular organ were devoid of specific staining. By late prometamorphosis, labeled fibers from the suprachiasmatic nucleus were observed projecting caudally to enter the hypothalamo-hypophysial-tract en route to innervating the median eminence and pituitary. Labeled fibers arising from the dorsal infundibular nucleus projected ventrolaterally to contribute to catecholaminergic innervation of the median eminence and pituitary. Immunoperoxidase staining of tyrosine hydroxylase-immunoreactive fibers and terminal arborizations in the median eminence were restricted to non-ependymal layers, while labeled fibers in the pituitary were observed in the pars intermedia and pars nervosa. Staining of tyrosine hydroxylase-immunoreactive fibers in the median eminence and pituitary was sparse or absent in premetamorphic tadpoles, but became increasingly more intense as metamorphosis progressed.     

Ontogeny of vasopressin and oxytocin in the fetal rat: Early vasopressinergic innervation of the fetal brain

The content and distribution of vasopressin and oxytocin were determined during fetal development in the rat brain and pituitary by means of radioimmunoassay and immunocytochemistry. The vasopressin content in the fetal brain showed a gradual rise from day 16 of pregnancy onwards, while pituitary vasopressin rapidly increased from fetal day 19 until birth. The oxytocin content in the fetal brain was considerably lower than the vasopressin content. A decrease in oxytocin content was seen between day 16 and day 18 while from day 18 of pregnancy onwards a slight increase was found. The pituitary oxytocin content starts to rise between day 17 and 18 of pregnancy, but at term the pituitary oxytocin content was only 1/20 of the vasopressin value. Immunocytochemistry revealed that vasopressin levels in the fetal rat brain were not only due to the presence of the classical hypothalamoneurohypophyseal system, but also to the early development of exohypothalamic fibers. Vasopressin containing cells were seen from fetal day 16 in the supraoptic nucleus, and from fetal day 18 in the paraventricular nucleus. The fiber outgrowth of these cells towards the pituitary and extrahypothalamic brain sites seems to be well synchronized, as on day 17 vasopressin containing fibers could be demonstrated in the olfactory bulb as well as in the median eminence. No positive staining for oxytocin could be obtained in the fetal rat, while during the entire fetal period no positive staining was found in cell bodies in the region of the suprachiasmatic nucleus. The early peptidergic innervation of the brain, which enabled the tracing of the source of some exohypothalamic fibers, might be related to several central processes among which brain development itself is included.     

Ontogeny of vasopressin and oxytocin in the fetal rat: Early vasopressinergic innervation of the fetal brain

The content and distribution of vasopressin and oxytocin were determined during fetal development in the rat brain and pituitary by means of radioimmunoassay and immunocytochemistry. The vasopressin content in the fetal brain showed a gradual rise from day 16 of pregnancy onwards, while pituitary vasopressin rapidly increased from fetal day 19 until birth. The oxytocin content in the fetal brain was considerably lower than the vasopressin content. A decrease in oxytocin content was seen between day 16 and day 18 while from day 18 of pregnancy onwards a slight increase was found. The pituitary oxytocin content starts to rise between day 17 and 18 of pregnancy, but at term the pituitary oxytocin content was only of the vasopressin value. Immunocytochemistry revealed that vasopressin levels in the fetal rat brain were not only due to the presence of the classical hypothalamoneurohypophyseal system, but also to the early development of exohypothalamic fibers. Vasopressin containing cells were seen from fetal day 16 in the supraoptic nucleus, and from fetal day 18 in the paraventricular nucleus. The fiber outgrowth of these cells towards the pituitary and extrahypothalamic brain sites seems to be well synchronized, as on day 17 vasopressin containing fibers could be demonstrated in the olfactory bulb as well as in the median eminence. No positive staining for oxytocin could be obtained in the fetal rat, while during the entire fetal period no positive staining was found in cell bodies in the region of the suprachiasmatic nucleus. The early peptidergic innervation of the brain, which enabled the tracing of the source of some exohypothalamic fibers, might be related to several central processes among which brain development itself is included.     

Location of neurons projecting to the hypophysial stalk — median eminence in ring doves (Streptopelia roseogrisea)

The median eminence/pituitary stalk represents the final common pathway for fibers from neurons that project to the pituitary gland. We have used the lipophilic fluorescent tracer 1,1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanine perchlorate (DiI) to determine the location of neurons projecting to the median eminence/pituitary stalk in ring doves. The tracer can be precisely applied to fixed tissue, in areas to which it is otherwise difficult to gain access. Follwwing application of DiI to the median eminence/pituitary stalk, labeled neurons were detected in six distinct regions: the ventromedial hypothalamic nucleus, paraventricular nucleus, supraoptic nucleus, in and ventral to the lateral forebrain bundle, preoptic area, and lateral septum. Labeled fibers branched extensively in the diencephalon, particularly along the third ventricle and in the septal-preoptic area. Sparse fiber labeling occurred caudal to the tuberal hypothalamus, even though these regions were close to the application site of the tracer. Labeled cerebrospinal-fluid-contacting cells were seen in the paraventricular region of the third ventricle. The results indicate that the avian neuronal system that projects to the median eminence and neural lobe occurs in diffuse clusters largely along the midline region of the hypothalamic septal-preoptic area. The paucity of fiber staining caudal to the tuberal hypothalamic region indicates that cells of these regions do not project to the median eminence/pituitary.     

Efferent projections from the lateral geniculate nucleus to the pineal complex of the Mongolian gerbil (Meriones unguiculatus)

Summary The intergeniculate leaflet of the lateral geniculate nucleus is considered to modulate circadian activity rhythms probably mediated by a direct neuronal connection to the suprachiasmatic nucleus. The present study in the gerbil demonstrates, by anterograde tracing with Phaseolus vulgaris-leucoagglutinin (PHA-L), the existence of an additional neuronal projection from a subportion of the lateral geniculate nucleus, involving the intergeniculate leaflet, directly to the pineal gland. PHA-L-immunoreactive nerve fibers originating from perikarya at the injection site were located under the optic tract projecting towards the midsagittal plane. Delicate PHA-L-immunoreactive nerve fibers were observed in the posterior paraventricular thalamic nucleus, precommissural nucleus, olivary pretectal nucleus, anterior and posterior pretectal nuclei, and posterior commissure. Single fibers could be followed from the caudal part of the medial habenular nucleus and the pretectal area into the rostral part of the deep pineal gland. Other fibers continued through the posterior commissure into the contralateral hemisphere to terminate in the same structures as on the ipsilateral side. From the posterior commissure, small bundles of thick fibers entered the deep pineal gland where they arborized among the endocrine cells. A few nerve fibers were observed in the habenular commissure and the pineal stalk, but no fibers were identified in the superficial pineal. This direct geniculo-pineal connection suggests that the pineal gland is directly influenced by the optic system.     

Hypothalamic lesions stimulating growth hormone cell activity in the goldfish

Summary The cytology of the growth-hormone (GH) cells of the goldfish pituitary were examined following electrothermic lesions of the anterior praeoptic hypothalamus and telencephalon. Following lesions of the nucleus preopticus (NPO) light microscopy of the pituitary revealed a significant increase in the nuclear diameter and a degranulation of the GH cells. Lesions of the telencephalon anterior or dorsal to the NPO had no cytological effect on the GH cells. The ultrastructural appearance of the GH cells of NPO-lesioned fish was characterized by a marked degranulation of the cytoplasm and a proliferation of the rough endoplasmic reticulum indicative of enhanced secretory activity. The GH cells of the proximal pars distalis (PPD) are directly innervated by peptidergic (type A) and aminergic-like (type B) neurosecretory axons. Following lesions of the NPO, there was a marked reduction in the number of type A fibers in the PPD. These results suggest that the type A fibers innervating the GH cells originate in the NPO and act to inhibit the secretory activity of the GH cells.     

The distribution of gonadotropin-releasing hormone (GnRH) neurons and fibers throughout the chick brain (Gallus domesticus)

Summary Nerve fibers and perikarya containing gonadotropin-releasing hormone (GnRH-like) immunoreactivity were investigated in the brain of the three-week-old chick, Gallus domesticus using the technique of immunocytochemistry. Six major groups of perikarya were found to include the olfactory bulb, olfactory tubercle/lobus parolfactorius, nucleus accumbens, septal preoptic hypothalamic region (three sub-nuclei), lateral anterior thalamic nucleus and in and about the oculomotor complex. The immunostaining was unusual in the latter group, suggesting that the neurons may contain a GnRH-II like material. Immunoreactive fibers for GnRH were found throughout the entire brain extending from the olfactory bulbs to the caudal brainstem. Two anatomical areas, not emphasized in the past literature, which had distinct GnRH-like immunoreactivity, included the lateral anterior thalamic nucleus and the preoptic recess. The former included a group of GnRH perikarya that is also known to be a retino-recipient area while the latter contained neuronal terminals some of which appeared to be contacting the cerebrospinal fluid of the preoptic recess. An attempt was made to list all anatomical structures that contained or were juxta-positioned to sites that displayed immunoreactive perikarya and fibers including circumventricular organs.Abbreviations used in figure legends Ac Nucleus accumbens - Ap Archistriatum posterior - APH Area parahippocampalis - AVT Area ventralis (Tsai) - BO Bulbus olfactorius - CA Commissura anterior (rostralis) - CDL Area corticoidea dorsolateralis - CO Chiasma opticum - CP Commissura posterior - CPi Cortex piriformis - CPP Cortex praepiriformis - CT Commissura tectalis - CTz Corpus trapezoideum - EW Nucleus of Edinger-Westphal - FV Funiculus ventralis - GCt Substantia grisea centralis - GLv Nucleus geniculatus lateralis, pars ventralis - HD Hyperstriatum dorsale - HM Nucleus habenularis medialis - Hp Hippocampus - ICo Nucleus intercollicularis - IH Nucleus inferior hypothalami - IN Nucleus infundibuli hypothalami - IP Nucleus interpeduncularis - LA Nucleus lateralis anterior (rostralis) thalami - LHy Regio lateralis hypothalami - LPO Lobus parolfactorius - LSO Organum septi lateralis (lateral septal organ) - LT Lamina terminalis - ME Eminentia mediana - INT. Z Internal zone - EXT. Z External zone - ML Nucleus mamillaris lateralis - MM Nucleus mamillaris medialis - nBOR Nucleus opticus basalis (n. of basal optic root) - nCPa Nucleus commissurae pallii - N III Nervus oculomotorius - N V Nervus trigeminus - n V M Nucleus mesencephalicus nervi trigemini - OA Nucleus olfactorius anterior (rostralis) - OMdl Nucleus nervi oculomotorii, pars dorsomedialis - OMv Nucleus nervi oculomotorii, pars ventralis - OVLT Organum vasculosum laminae terminalis - P Glandula pinealis - PA Palaeostriatum augmentatum (caudate putamen) - PHN Nucleus periventricularis hypothalami - POM Nucleus praeopticus medialis - POMn Nucleus praeopticus medianus - POP Nucleus praeopticus periventricularis - PP Palaeostriatum primitivum - PT Nucleus praetectalis - PVN Nucleus paraventricularis magnocellularis - RPaM Nucleus reticularis paramedianus - RPR Recessus praeopticus - b, RPR Basal region, RPR - F, RPR Floor, RPR - R, RPR Roof, RPR - S Nucleus tractus solitarii - SCO Organum subcommissurale - SGP Stratum griseum periventriculare - SHL Nucleus subhabenularis lateralis - SL Nucleus septalis lateralis - SM Nucleus septalis medialis - SO Stratum opticum - SSO Organum subseptale - TO Tuberculum olfactorium - TIO Tractus isthmo-opticus - TPc Nucleus tegmenti pedunculopontinus, pars compacta (substantia nigra) - TrO Tractus opticus - TSM Tractus septomesencephalicus - VeD Nucleus vestibularis descendens - VeM Nucleus vestibularis medialis - VL Ventriculus lateralis - VLT Nucleus ventrolateralis thalami - VO Ventriculus olfactorius - V III Ventriculus tertius (third ventricle)     

Localization of corticotropin-releasing hormone (CRF)-like immunoreactivity in the central nervous system of the elasmobranch fish,Scyliorhinus canicula

Summary The occurrence and localization of immunoreactive corticotropin-releasing factor (CRF) in the brain and pituitary of the elasmobranch fish Scyliorhinus canicula, were studied by means of specific radioimmunoassay and immunohistochemistry using the indirect immunofluorescence method. Brain and pituitary extracts showed a good cross-reactivity with the ovine CRF antiserum, but serial dilutions of tissue samples did not completely parallel the standard curve. Relatively high concentrations of CRF-like material were found within the pituitary, diencephalon, and telencephalon. CRF-like immunoreactive perikarya were observed in the preoptic nucleus and in the nucleus lateralis tuberis. Numerous immunoreactive cells appeared to be of the CSF-contacting type. CRF-like immunopositive fibers were seen to run through the hypothalamus within the ventro-medial floor of the infundibular region. A dense plexus of immunoreactive nerve endings terminated in the median eminence and the neurointermediate lobe of the pituitary. These results indicate that a neurosecretory system containing CRF-like immunoreactivity exists in the brain of elasmobranchs, a group of vertebrates which has diverged early from the evolutionary line leading to mammals. In addition, our data support the notion that a CRF-like molecule is involved in the regulation of corticotropic and melanotropic cell activity in this primitive species of fish.     

Distribution pattern in the human pituitary and hypothalamus of a new neuropeptide: The C-terminal glycoprotein-fragment of human pro-pressophysin (CPP)

Summary The distribution pattern of CPP-containing neurons and fibers in the human pituitary and hypothalamus was studied with a specific antiserum to human CPP and the unlabeled antibody technique. Immunoreactive CPP was found in the magnocellular neurons of the supraoptic nucleus (SON), the paraventricular nucleus (PVN) and in neurons scattered in the supraoptic hypophyseal tract. CPP-containing parvocellular neurons were found in the suprachiasmatic nucleus (SCN). The CPP-containing fibers from the magnocellular neurons formed a tract coursing through the median eminence and the pituitary stalk to the posterior lobe of the hypophysis. In contrast, no such fibers from the SCN projected to SON, PVN and the median eminence. This pattern is identical to that of vasopressin and its associated neurophysin-containing neurons and fibers and strongly supports the concept that CPP is a part of the common precursor for vasopressin and neurophysin II. The biological importance of human CPP other than being a precursor fragment remains to be elucidated.To whom requests for reprints should be addressed     

Corticotropin-releasing hormone in the human hypothalamus. Free-floating immunostaining method

We have clearly demonstrated corticotropin-releasing hormone (CRH) immunoreactive cell bodies and nerve fibers in the human hypothalamus by immunocytochemistry using free-floating sections instead of paraffin-embedded sections. Human hypothalami were obtained at autopsy, fixed and cryostat-sectioned at 40 microns. Free-floating sections were immunostained with antibody to CRH using the Vector ABC system. Most of CRH immunoreactive nerve fibers from the paraventricular nucleus pass under the fornix, while some CRH immunoreactive nerve fibers pass beyond the fornix and some through the fornix. Then the CRH immunoreactive nerve fibers run downward, medially to the supraoptic nucleus and toward the pituitary stalk. This method of immunocytochemistry is a very sensitive and suitable means for immunocytochemical studies of neuropeptides in the human brain.     

Development of melanin-concentrating hormone-immunoreactive elements in the brain of gilthead seabream (Sparus auratus)

The development of the hypothalamic melanin-concentrating hormone (MCH) system of the teleost Sparus auratus has been studied by immunocytochemistry using an anti-salmon MCH serum. Immunoreactive perikarya and fibers are found in embryos, larvae, and juvenile specimens. In juveniles, most labeled neurons are present in the nucleus lateralis tuberis; some are dispersed in the nucleus recessus lateralis and nucleus periventricularis posterior. From the nucleus lateralis tuberis, MCH neurons project a conspicuous tract of fibers to the ventral hypothalamus; this penetrates the pituitary stalk and reaches the neurohypophysis. Most fibers end close to the cells of the pars intermedia, and some reach the adenohypophysial rostral pars distalis. Immunoreactive fibers can also be seen in extrahypophysial localizations, such as the preoptic region and the nucleus sacci vasculosi. In embryos, MCH-immunoreactive neurons first appear at 36 h post-fertilization in the ventrolateral margin of the developing hypothalamus. In larvae, at 4 days post-hatching, perikarya can be observed in the ventrolateral border of the hypothalamus and in the mid-hypothalamus, near the ventricle. At 26 days post-hatching, MCH perikarya are restricted to the nucleus lateralis tuberis. The neurohypophysis possesses MCH-immunoreactive fibers from the second day post-hatching. The results indicate that MCH plays a role in larval development with respect to skin melanophores and cells that secrete melanocyte-stimulating hormone. Received: 4 April 1995 / Accepted: 17 July 1995     

Immimohistochemical localization of corticotropin-releasing factor in selected brain areas of the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia)

Summary Corticotropin-releasing factor (CRF) was localized in the brains of two passerine species, the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia), by means of immunohistochemistry. The hypothalamic distribution of this peptide in these species includes a complex of immunoreactive perikarya observed in the paraventricular nucleus (PVN), in both its medial and lateral divisions. Nerve fibers were also seen running from these areas to the anterior median eminence (AME) where a terminal field is apparent. A wide variety of extra-hypothalamic nuclei containing CRF-immunoreactive cells and fibers were identified. An apparent CRF terminal field can be visualized in the lateral septum. A dense fiber plexus is present in the nucleus accumbens (Ac) and more caudally in the nucleus of the stria terminalis (nST). In colchicinepretreated animals, it was revealed that these areas also contain CRF-stained perikarya. The pattern of CRF immunoreactivity in the Ac-nST complex is continuous, with no distinction apparent between the nuclei. The medial preoptic area (mPOA) and the adjacent diagonal band of Broca contain CRF-fibers, while cells are apparent in the mPOA. In the mesencephalon, cells were visualized in the midbrain central gray; a terminal field and scattered positively stained perikarya were found in areas more ventral to the central grey that are adjacent to the third cranial nerve. Scattered cells were also seen at the border of the nucleus intercollicularis-nucleus mesencephalicus lateralis, pars dorsalis complex. In contrast to mammalian studies, no immunoreactive nerve fibers or perikarya were observed in telencephalic areas homologous to the mammalian neocortex. These studies confirm the presence of a CRF path-way regulating pituitary function and suggest a broad role played by CRF as a neuromodulator or neurotransmitter in autonomic and possibly behavioral activities in these species.     

Immunoreactive gonadotropin-releasing hormone (GnRH) in the brain and pituitary of adult and juvenile swordtails (Xiphophorus helleri,Teleostei, Poeciliidae)

Different molecular variants of gonadotropin-releasing hormone (GnRH) were localized in the brain and pituitary of Xiphophorus helleri, from neonates up to mature animals of both sexes. Nine GnRH antisera to salmon (s), mammalian (m), chicken I (c-I), and chicken II (c-II) GnRH were utilized. In the first week after birth GnRH immunoreactivity (IR) emerges with pale staining of the nucleus olfactoretinalis (NOR) in the ventral forebrain. The intensity of IR in the NOR increases during the next weeks and an IR tract of nerve fibers appears, protruding from the NOR in dorsocaudal direction. Adult animals exhibit additional GnRH-positive structures. Some perikarya of the nucleus preopticus periventricularis (NPP) are IR and positive fibers extend from the NPP toward the pituitary. In the pituitary IR fibers are also detectable. A distinctive structure in adult animals is an IR cord of neurons (CN) at the bottom of the forebrain which extends from the NPP to the olfactory nerve. A comparison of antisera against different GnRH species indicates that sGnRH is present in the NOR, whereas a different form of GnRH is present in the NPP, CN, and pituitary. The early onset of GnRH IR in the NOR and the widespread distribution of positive fibers from that nucleus into other brain regions suggest neuromodulatory functions of sGnRH from the NOR. The NPP possibly plays a major role in direct stimulation of pituitary gonadotropes via a different type of GnRH. © 1996 Wiley-Liss, Inc.