Beta-endorphin-like immunoreactivity in the forebrain and pituitary of the teleost Clarias batrachus (Linn.)

The organization of beta-endorphin-like immunoreactivity in the olfactory system, forebrain, and pituitary of the teleost Clarias batrachus was investigated. Immunoreactivity was prominently seen in the sensory neurons and basal cells in the olfactory epithelium and in some cells in the periphery and center (granule cells) of the olfactory bulb. Immunoreactive fibers in the olfactory nerve enter the olfactory nerve layer of the olfactory bulb and branch profusely to form tufts organized as spherical neuropils in the glomerular layer. While fascicles of immunoreactive fibers were seen in the medial olfactory tracts, the lateral olfactory tracts showed individual immunoreactive fibers. Immunoreactive fibers in the medial olfactory tract extend into the telencephalon and form terminal fields in discrete telencephalic and preoptic areas; some immunoreactive fibers decussate in the anterior commissure, while others pass into the thalamus. While neurons of the nucleus lateralis tuberis revealed weak immunoreactivity, densely staining somata were seen at discrete sites along the wall of the third ventricle. Although a large population of immunoreactive cells was seen in the pars intermedia of the pituitary gland, few were seen in the rostral pars distalis and proximal pars distalis; immunoreactive fibers were seen throughout the pituitary gland.     

Glucagon-like immunoreactivity in the forebrain and pituitary of the teleost, Clarias batrachus (Linn.)

The organization of glucagon-like immunoreactivity (GLI) in the olfactory system, forebrain, and pituitary was investigated in the teleost Clarias batrachus. Weak to moderate GLI was seen in some olfactory receptor neurons and basal cells of the olfactory epithelium. Intense GLI was seen in the olfactory nerve fascicles that ran caudally to the bulb, spread over in the olfactory nerve layer, and profusely branched in the glomerular layer to form tufts organized as spherical neuropils; some of the immunoreactive fibers seem to closely enfold the mitral cells. In the inner cell layer of the bulb, some granule cells were intensely immunoreactive. Although there were thick fascicles of immunoreactive fibers in the medial olfactory tracts (MOT), the lateral olfactory tracts were generally devoid of immunoreactivity. Immunoreactive fibers in the medial olfactory tract penetrated into the telencephalon from its rostral pole and entered into the area ventralis telencephali/pars ventralis where the compact fiber bundles loosen somewhat and course dorsocaudally into the area ventralis telencephali/pars supracommissuralis just above the anterior commissure. While some immunoreactive fibers decussated in the anterior commissure, fine fibers were seen in the commissure of Goldstein. Isolated immunoreactive fibers of the medial olfactory tract were traced laterally into the area dorsalis telencephali/pars lateralis ventralis and mediodorsally into the area dorsalis telencephali/pars medialis. However, a major component of the MOT continued dorsocaudally into the thalamus and terminated in the habenula. Two immunoreactive neuronal groups and some isolated cells were seen in the periventricular region of the thalamus. Although nucleus preopticus showed no immunoreactivity, some neurons of the nucleus lateralis tuberis displayed moderate GLI. Several immunoreactive cells were seen in the pars intermedia of the pituitary gland; few were encountered in the rostral pars distalis and proximal pars distalis. Immunoreactive fibers were seen throughout the pituitary gland.     

Effects of hypothalamic and thalamic lesions on prolactin secretion in goldfish (Carassius auratus)

The effects of hypothalamic and thalamic lesions on serum and pituitary prolactin levels in goldfish were studied. A radioimmunoassay was used to measure prolactin levels. Lesions in the nucleus lateral tuberis (NLT) pars anterioris, NLT pars posterioris, NLT pars inferioris, nucleus anterior tuberis, or in the nucleus preopticus did not affect serum or pituitary polactin levels compared to sham or normal control groups. Lesions in the NLT pars lateralis caused a significant increase in serum prolactin, but had no effect on pituitary prolactin levels. This suggests that the NLT pars lateralis is the origin of a factor that normally inhibits prolactin release from the pituitary. Large lesions that destroyed the medial thalamic and anterior hypothalamic region dorsal to the NLT caused a significant decrease in serum prolactin, but had no significant effect on pituitary prolactin levels. It is suggested that the lesions in this region may have interrupted neural afferents to the NLT pars lateralis that normally inhibit secretion of a prolactin inhibitory factor.     

beta-endorphin and gonadotropin-releasing hormone in the forebrain and pituitary of the female catfish, Clarias batrachus: double-immunolabeling study

The role of beta-endorphin in modulating the gonadotropic action of gonadotropin-releasing hormone (GnRH) is well established in mammals. Although the information from teleosts also suggests that endogenous opioids modulate GnRH secretion and influence gonadotropic hormone release, the anatomical substrate in which opiate peptides and GnRH may interact has not been studied. Herein we describe the mammalian GnRH- and beta-endorphin-like immunoreactivities in the olfactory system, forebrain, and pituitary of the teleost, Clarias batrachus, using the double immunocytochemical method. While several olfactory receptor neurons showed beta-endorphin- or GnRH-like immunoreactivity, some neurons with dual immunoreactivities were also seen. GnRH- and/or beta-endorphin-like immunolabeled fascicles were seen in the olfactory nerves as they run caudally to the olfactory bulb and spread in the periphery. Several fascicles branch profusely to form tufts organized as spherical neuropils in the glomerular layer. Frequently, the innervation of the glomeruli showed a distinct pattern. While the fascicles on the medial side showed a predominance of beta-endorphin-like fibers, the majority of the fascicles on the lateral side of the bulb showed dual immunoreactivities. Several GnRH- and beta-endorphin-like immunoreactive fibers were seen in the medial olfactory tract as it extends through the telencephalon in the area ventralis telencephali/pars supracommissuralis; individual fibers with dual staining were also seen. The nucleus lateralis tuberis showed beta-endorphin- as well as GnRH-like immunoreactive neurons. While GnRH-containing cells were seen in the proximal pars distalis and pars intermedia, beta-endorphin-like cells were located throughout the pituitary; some cells in the pars intermedia showed dual immunoreactivity. The high degree of overlapping suggests the possibility of profound interplay between GnRH- and beta-endorphin-like immunoreactive systems at different levels of the neuraxis.     

Melanin-concentrating hormone (MCH) immunoreactive hypophysial neurosecretory system in the teleost Poecilia latipinna: light and electron microscopic study

Neurons containing immunoreactivity for melanin-concentrating hormone (MCH) were located in the brain of the teleost Poecilia latipinna by light microscopic (peroxidase antiperoxidase) and electron microscopic (immunogold) methods. Neuronal cell bodies were found in the tuberal hypothalamus, mostly within the nucleus lateralis tuberis, pars lateralis, containing MCH-immunoreactive granules up to 150 nm in diameter. From here bundles of immunoreactive fibers could be traced through the preoptic area as far forward as the olfactory bulb, and through the posterior hypothalamus up into the pretectal thalamus and midbrain. The main projection was, however, to the neurohypophysis, where MCH fibers were observed to form contacts with pituicytes, basement membranes around blood vessels, and the endocrine cells of the pars intermedia. Occasionally MCH-immunoreactive terminals were also seen near the corticotrophs of the rostral pars distalis. These results support the hypothesis that MCH may act as a systemic hormone, a central neurotransmitter, and a modulator of pituitary function.     

Immunocytochemical localization of LH-RH in the brain and pituitary of the catfish, Clarias batrachus (Linn.)

An elaborate organization of luteinizing hormone-releasing hormone (LH-RH) immunoreactive (ir) cells and fibers was encountered in the olfactory system of Clarias batrachus. In addition to the ir structures in the olfactory nerve, peripheral area of the olfactory bulb, and the medial olfactory tract (MOT), ir cells and fibers were prominently seen in the lamellae of the olfactory organ. Perikarya showing varying degrees of intensity of immunoreaction were observed along the base of the forebrain in the nucleus preopticus basalis lateralis, nucleus preopticus periventricularis, nucleus preopticus, nucleus lateralis tuberis pars posterior, and the pituitary. Some cells were also noticed in the midbrain tegmentum. A well-defined system of ir fibers from the MOT penetrated the telencephalon and curved dorsocaudally into the pars supracommissuralis above the anterior commissure (AC); while some fibers decussate in the AC, others extended posteriorly into the diencephalon. A fairly dense network of beaded ir fibers was seen in the basal forebrain, conspicuous around the organum vasculosum laminae terminalis and caudally traceable as far as the neurohypophysis; some immunostained fibers appear to be directly contacting with the cells of the proximal pars distalis. Fibers were also witnessed in the optic chiasma and in the inner plexiform layer of the retina. Solitary fibers were noticed in certain circumscribed telencephalic areas, caudal hypothalamus, posterior commissure, midbrain tegmentum, cerebellum, and ventral medulla oblongata. The highly organized LH-RH containing system in C. batrachus is indicative of its elaborate role in synchronization of the reproductive processes and the environmental cues.     

Immunocytochemical study on the localization and distribution of the somatolactin cells in the pituitary gland and the brain of Oreochromis niloticus (Teleostei, cichlidae)

Using specific antibody for chum salmon somatolactin (SL), immunocytochemical studies were employed to determine the distribution of this hormone in the pituitary gland and the brain of Orechromis niloticus. The results indicated that the SL-immunoreactive (ir) cells are found in the pars intermedia (PI) of the pituitary gland. The SL-ir cells showed strong and specific immunoreactivity to anti-chum salmon SL. Moreover, SL-ir cells were found to be widely distributed in most brain regions. Most of the SL-ir cell bodies were scattered along a nearly continuous line extending posteriorly from the olfactory bulb to the medulla oblongata through the nucleus preopticus periventricularis, habenula, and midbrain tegmentum and ventral to the nucleus lateralis tuberis pars posterior through the nucleus preopticus basalis lateralis and organum vasculosum luminae terminalis. Also SL-ir cells were observed in the cerebellum. The synthetic and secretory activity of the SL-ir cells, in the pituitary and the brain, showed an increase during sexual maturation and spawning. The highly organized SL-containing system and the gradual stimulation of SL synthesis and release during sexual maturation and spawning of O. nilotcus suggest that SL may be involved in the control of some steps of reproductive processes.     

Localization of growth hormone releasing factor-like immunoreactivity in the hypothalamo-hypophyseal system of the frog (Rana temporaria) and the sea bass (Dicentrarchus labrax)

Using two different antisera, one raised against total human pancreatic growth hormone releasing factor (hpGRF) coupled through a two-step glutaraldehyde method and the other one raised against rat hypothalamic growth hormone releasing factor 1-10 (rGRF1-10), GRF-like immunoreactivity was localized in the hypothalamo-hypophyseal system of the frog (Rana temporaria) and the sea bass (Dicentrarchus labrax). In the frog immunoreactive neurons were found in the nucleus preopticus, pars magnocellularis. The immunopositive fibers were localized in the lateral wall of the preoptic recess, the pars ventralis of the tuber cinereum, the internal and external zone of the median eminence, and the neural lobe. Positive-stained neurons in the sea bass were located in the preoptic nucleus, in the pars magnocellularis as well as in the pars parvocellularis, and in the nucleus lateralis tuberis, pars rostralis. GRF-ir nerve fibers, originating in the hypothalamus, projected to the rostral and proximal pars distalis, the posterior neurohypophysis, and the pars intermedia (PI). Double stainings with anti-GRF and anti-ACTH or anti-trout GH showed some close relationship between GRF immunoreactive nerve fibers and adenohypophyseal cell types. In the PI both the MSH and the PI "PAS" positive cells seemed to be directly innervated by the GRF-ir axons. These results show that a GRF-like system is present in the hypothalamo-hypophyseal system of amphibians and teleosts and that in these lower vertebrates GRF-like material may be secreted directly in the systemic circulation. The function of this GRF, however, is not yet clear.     

Somatotropin Release-Inhibiting Factor and Galanin Innervation in the Hypothalamus and Pituitary of Seabream (Sparus aurata)

The distribution of galanin (GAL) and somatotropin-release-inhibiting-factor (SRIF) immunoreactivity in the hypothalamus and pituitary of the sea bream (Sparus aurata) was studied by immunocytochemistry. An extensive system of neurons immunoreactive with antisera to the two peptides was identified throughout the brain with staining particularly in the hypothalamus. In the hypothalamus, GAL immunoreactive perikarya were detected principally in the nucleus preopticus and nucleus tuberis. Major nerve tracts were observed to sweep down from the hypothalamic nuclei and reached the pituitary via the preoptico-hypophysial tract. Many of the fibers had varicose swellings indicating they were secretory. SRIF immunoreactivity was distributed similarly to GAL but the network of nerve fibers was less dense; no colocalization of these two peptides was seen. SRIF immunoreactive perikarya were present in the preoptic nucleus, the tuberal nucleus, and the basolateral hypothalamus. These perikarya were large and densely staining and were predominately bipolar, although some multipolar perikarya were observed. In the pituitary GAL and SRIF immunoreactivities were confined principally to the pars distalis where fibers infiltrated between growth hormone, prolactin, and adrenocorticotrophic cells. More of the fibers were immunoreactive for SRIF than for GAL. There was no immunoreaction for GAL or SRIF in any of the pituitary cells. There is thus morphological evidence for a neuroendocrine control of the pars distalis by GAL and SRIF and for a possible functional interaction between these two systems.     

Comparative distribution of somatostatin, LH-RH, neurophysin, and alpha-endorphin in the rainbow trout: an immunocytological study.

Using immunofluorescence, evidence of a somatostatin (SRIF)-like antigen has been found in the brain and digestive tract of rainbow trout. In the diencephalon, periventricular SRIF immunoreactive hypendymocytes are located in the region dorsal to the nucleus preopticus (NPO). SRIF immunoreactive perikarya are concentrated anterior to the NPO in the nucleus preopticus periventricularis, scattered in small cells in the nucleus lateralis tuberis (NLT) pars anterior, and in a few cells located in an unnamed nucleus in the dorsomedial hypothalamus. In the pituitary SRIF immunoreactive material is located in the neurohypophysial tissue in the proximal pars distalis. In the gut, SRIF cells have been found in the endocrine pancreas and in the gastric mucosa. Comparatively, material immunoreactive for luteinizing hormone-releasing hormone has the same distribution in the pituitary as SRIF, whereas neurophysin immunoreactivity was found in only the neurophysial tissue of the neurointermediate lobe. A few cells reacting with anti-α-endorphin were seen in the NLT in the pituitary stalk region. All the pars intermedia cells in the neurointermediate lobe react with anti-α-endorphin.     

Immunohistochemical localization of corticotropin-releasing factor in the brain and corticotropin-releasing factor and thyrotropin-stimulating hormone in the pituitary of chinook salmon (Oncorhynchus tshawytscha)

This report describes the distribution of corticotropin-releasing factor (CRF)-like immunoreactivity in the brain and the contiguous localization of CRF- and thyrotropin-stimulating hormone (TSH)-like immunoreactivity in the pituitary of hatchery-reared, juvenile chinook salmon (Oncorhynchus tshawytscha). Results show that CRF-immunoreactive cell bodies exist in the parvocellular and magnocellular nuclei of the preoptic area and in a ventral hypothalamic region corresponding to the nucleus lateralis tuberis. CRF-immunoreactive fibers are observed along the rostral edge of the hypothalamus, in the pituitary stalk, and in the pituitary gland. Within the pituitary, CRF-immunoreactive fibers, with terminal-like boutons, were distinguishable in the neurohypophysis, pars distalis (PD), and pars intermedia (PI). In the PD, the CRF-immunoreactive fibers terminate in regions that contain TSH-positive pituitary cells. From this study, we conclude that CRF-immunoreactive fibers travel through, and terminate in, the neurohypophysis. CRF-immunoreactive fibers were also observed to terminate within the basement membrane and within the PD and PI of the adenohypophysis. Furthermore, the contiguous localization of CRF-immunoreactive fibers and TSH-immunoreactive pituitary cells suggests that CRF may mediate release of TSH.     

Thyrotropin-releasing hormone (TRH): Immunohistochemical distribution in tadpole and frog brain

The anatomical localization of immunoreactive TRH (IR-TRH) was demonstrated by the peroxidase-antiperoxidase technique in the brain and pituitary gland of larval and adult Rana catesheiana. In the adult frog main sites of IR-TRH are perikarya and neuronal fibers in the preoptic and infundibular nuclei of the hypothalamus and in the amygdala and diagonal band of Broca of the telencephalon. In addition, TRH-positive neuronal fibers and endings were found in the septum, pallium, and brain stem as well as in the preoptico-hypophyseal tract, the external zone of the median eminence (which matures during late larval stages), and the pars nervosa; fibers were less extensive in the pars intermedia, and were absent from the pars distalis. In early larval stages, the magnocellular nucleus of the posterior preoptic area is the main site of immunoreactive perikarya. During late stages the extensive adult pattern of distribution of IR-TRH becomes established. The study represents the first immunohistochemical demonstration of IR-TRH in larval anurans, and serves as a basis for clarification of the neuroendocrine regulation of metamorphosis.     

Effects of monosodium l-glutamate on pituitary innervation in goldfish, Carassius auratus

Monosodium l-glutamate was injected intraperitoneally into goldfish at a dosage of 2.5 mg/g body wt. The first noticeable effect in the pituitary, 30 min postinjection, was a marked swelling of pituicytes in the neurohypophysis (NH). Eighteen hours postinjection a large number of degenerating type B fibers were found in the NH of the proximal pars distalis (PPD), while all type A fibers, and type B fibers in other parts of the pituitary, remained unaffected. Because glutamate causes a lesion in the nucleus lateral tuberis (NLT), from the anterior margin of the pituitary stalk through to the posterior end of the nucleus, and a minor lesion in the nucleus preopticus periventricularis, it is likely that the NLT is the origin of the degenerative type B fibers in the proximal NH. The significance of these results is discussed in relation to the neuroendocrine regulation of the pituitary functions in goldfish.     

Relationship between serum growth hormone levels and the brain and pituitary content of immunoreactive somatostatin in the goldfish, Carassius auratus L

In this study, the relationships between endogenous brain and pituitary immunoreactive somatostatin (irSRIF) and circulating growth hormone (GH) levels in the goldfish were examined using two approaches. First, the amount of irSRIF in extracts of the pituitary gland and various brain regions was measured by radioimmunoassay several times throughout the year and was compared to serum GH levels at each time. The amounts of irSRIF in extracts of the pituitary gland, hypothalamus, and telencephalon were found to be inversely related to seasonal changes in serum GH levels, such that irSRIF was highest in these regions when serum GH levels were lowest (November and February). Conversely, irSRIF in these regions was lower in May, June, and July when serum GH levels were highest. These results suggest that endogenous irSRIF in the pituitary and forebrain may participate in the regulation of seasonal changes in serum GH levels in the goldfish. In extracts from other brain regions (thalamus + midbrain and cerebellum + medulla), some changes in the amount of irSRIF were observed among the various sample times, but these variations were not related to changes in serum GH levels. In a second set of experiments, the origin of irSRIF fibers innervating the goldfish pituitary gland was examined by using brain lesioning techniques to destroy regions of the forebrain known to contain irSRIF perikarya and fibers, and subsequently measuring the amount of irSRIF in the pituitary gland. Lesions in the preoptic area of the forebrain resulted in increased serum GH levels concomitant with a decrease in pituitary irSRIF content. This provides direct evidence that the preoptic area is the origin of a somatostatinergic projection inhibiting GH secretion from the goldfish pituitary. Lesions centered in the nucleus lateral tuberis (NLT) pars anterioris did not influence serum GH levels or the pituitary content of irSRIF. In contrast, more posterior lesions centered in the NLT pars posterioris (NLTp) resulted in a dramatic reduction in the amount of irSRIF in the pituitary. This suggests that the majority of irSRIF projections to the goldfish pituitary pass through the area destroyed by the lesion centered in the NLTp; it is also possible that perikarya within this area may be the origin of at least some of the irSRIF-containing fibers in the goldfish pituitary. Together, results from the present study provide evidence of a functional relationship between circulating levels of GH and endogenous brain and pituitary irSRIF in the goldfish.     

Immunohistochemical localization of gonadotropin releasing hormones in the brain and pituitary gland of the Nile perch,Lates niloticus (Teleostei,Centropomidae)

In the present study we investigated the distribution of gonadotropin-releasing hormones (GnRH) in the brain of Lates niloticus and their association with different pituitary cell types using immunohistochemical techniques. We found immunoreactive (ir) chicken GnRH-II (cGnRH-II) and mammalian GnRH (mGnRH) as the main components of the GnRH-ir system within the brain of the Nile perch. The results indicate that mGnRH and cGnRH are localized in different neurons: mGnRH-ir perikaria were observed in the preoptic region particularly in the organum vasculosum laminae terminalis (OVLT) and in the nucleus lateralis tuberis pars posterior (NLTP) of the mediobasal hypothalamus. These cell bodies are located along a continuum of ir-fibers that could be traced from the olfactory nerve to the pituitary. mGnRH-ir fibers were detected in many parts of the brain (olfactory bulbs, ventral telencephalon, hypothalamus, and mesencephalon) and in the pituitary. cGnRH-ir cell bodies are restricted to the optic tract, but few scattered fibers could be detected in different parts of the brain. The pituitary exhibited very few cGnRH-II ir fibers, contrasting with an extensive mGnRH innervation. Moreover, mGnRH-ir fibers were targeting the three areas of the pituitary gland: rostral pars distalis (RPD), proximal pars distalis (PPD), and pars intermedia (PI). Double immunolabeling studies showed GnRH-ir fibers in close proximity with prolactin (PRL)- and adrenocorticotropic hormone (ACTH)-producing cells in the RPD, growth hormone (GH)-producing cells in the PPD, gonadotropins (GTHs)-producing cells in the PPD in the external border of the PI, and with somatolactin (SL)- and alpha-melanocyte stimulating hormone (alpha-MSH)-producing cells in the PI. Our results showed direct morphological evidence for a close association of GnRH-ir fibers with the different adenohypophysial cell types. These results suggest a multiple role of GnRH in the regulation of various pituitary hormones' release.     

FMRFamide-like immunoreactive nervus terminalis innervation to the pituitary in the catfish, Clarias batrachus (Linn.): demonstration by lesion and immunocytochemical techniques.

Certain thick FMRFamide-like immunoreactive fibers arising from the ganglion cells of nervus terminalis in the olfactory bulb of Clarias batrachus can be traced centripetally through the medial olfactory tract, telencephalon, lateral preoptic area, tuberal area, and hypothalamohypophysial tract to the pituitary. Following 6 days of bilateral olfactory tract transection, the immunoreactivity in the thick fibers, caudal to the lesion site, was partially eliminated, whereas after 10 and 14 days, it was totally abolished in the processes en route to the pituitary. The results indicate a direct innervation of the pituitary gland by the FMRFamide-like peptide containing fibers of the nervus terminalis.     

Immunocytochemical localization of growth hormone-releasing hormone-like peptide in the brain of the tiger frog,Rana tigrina

Using antisera directed against carp growth hormone-releasing hormone (cGHRH), we found more extensive brain distribution of GHRH-like immunoreactive (ir) neurons in the tiger frog, Rana tigrina, than reported in previous studies, which employed mammalian GHRH antibodies. In the telencephalon, GHRH-ir perikarya were present in the pallium dorsale, pallium laterale (pars dorsalis and pars ventralis), pallium mediale, nucleus entopeduncularis, amygdala pars medialis, and in the ventral portion of the lateral preoptic area. Most GHRH somata were present in the nucleus infundibularis ventralis located around the third ventricle, extending from the region posterior to the optic chiasma to the caudal end of infundibulum. In the thalamic region, GHRH-ir perikarya occurred in the area ventrolateralis thalami, the nuclei posterocentralis thalami, and the posterolateralis thalami. The ir cell bodies in the nucleus posteroventralis tegmenti mesencephali represented the caudal-most brain GHRH perikarya. Extensive GHRH-ir fibers occurred around the nonreactive cells in the ventral preoptic area and ventral area of the infundibulum. GHRH-ir fibers were present in the outer layers of the median eminence, but not in the neural lobe or pars distalis of the pituitary gland. This wider neuroanatomical distribution of GHRH-like peptide in the brain of R. tigrina should, provide the basis for future studies to establish the exact role of GHRH-like peptides in anuran brain.     

Immunohistochemical localization and radioimmunoassay of corticotropin-releasing factor in the forebrain and hypophysis of the frog Rana ridibunda

The distribution of immunoreactive corticotropin-releasing hormone (CRF) in the forebrain and pituitary of the frog Rana ridibunda was studied by means of specific radioimmunoassay and immunohistochemistry using the indirect immunofluorescence and the peroxidase-antiperoxidase techniques. Relatively high concentrations of CRF-like material were found in both chiasmatic and infundibular regions of the hypothalamus (352 +/- 11 and 422 +/- 36 pg, respectively). Large amounts of CRF were also found in neurointermediate lobe extracts. Standard curves of synthetic CRF and the dilution curves for hypothalamic or neurointermediate lobe extracts were parallel. After Sephadex G-75 gel filtration, CRF-like immunoreactivity eluted in a single peak, in the same position as synthetic ovine CRF. Reversed-phase high-performance liquid chromatography of the material purified on Sephadex G-75 revealed 5 components with CRF-like immunoreactivity. The major peak had a retention time of 22 min as compared to 25.4 min for ovine CRF and 36 min for rat CRF. The detection of CRF-like immunoreactivity in neurons was facilitated by colchicine pretreatment of the frogs. The great majority of the CRF-positive perikarya were seen in the ventral region of the preoptic nucleus. A few scattered perikarya were also observed in the dorsal preoptic nucleus and in the retrochiasmatic region. Immunoreactive fibers were found in the infundibular nucleus and in various extrahypothalamic zones. CRF-containing neurons were apparently distinct from mesotocinergic and vasotocinergic neurons. A large number of immunoreactive nerve fibers were observed in the median eminence in close contact with the capillaries of the pituitary portal plexus and in the neural lobe. A few CRF-positive fibers were detected in the intermediate lobe, whereas the distal lobe was totally negative. These results show that the diencephalon and pars intermedia-nervosa of the frog contain a peptide immunologically related to mammalian CRF.     

Immunocytochemical localization of luteinizing hormone-releasing hormone in the brain of the goldfish Carassius auratus

Using an indirect immunofluorescence technique, LH-RH was localized in the brain of the goldfish (Carassius auratus). Immunoreactive cell bodies were inconsistantly found in two hypothalamic nuclei: the anteroventral nucleus preopticus periventricularis (npp) and the posterior nucleus lateralis tuberis (nltp). Numerous immunoreactive fibers were observed in hypothalamic as well as in the extrahypothalamic parts of the brain and in the proximal pars distalis of the pituitary gland. Our results are discussed in relation to the neuroendocrine control of the pituitary gonadotropic function in teleosts.     

Marked distributional difference of alpha-melanocyte-stimulating hormone (alpha-MSH)-like immunoreactivity in the brain between two elasmobranchs (Scyliorhinus torazame and Etmopterus brachyurus): an immunohistochemical study

Application of alpha-MSH immunohistochemistry to the brain of elasmobranchs (Scyliorhinus torazame and Etmopterus brachyurus) demonstrated a marked species difference concerning the distribution of the alpha-MSH-like molecule in the brain. In S. torazame, alpha-MSH-like immunoreactive cells were present in the hypothalamus, mainly in the tuberculum posterius and the nucleus lateralis tuberis, and also in the distal and neurointermediate lobes of the hypophysis. Labeled varicose fibers were densely distributed in the hypothalamus, but they were sparse or absent in other portions of the brain. In striking contrast to the results for S. torazame, the immunoreactivity in the E. brachyurus brain was associated exclusively with the glial system, represented by astrocytes and tanycytes, throughout the central nervous system; no immunoreactivity was found in the neuronal elements. In the E. brachyurus hypophysis, the labeled cells were present in the distal and intermediate lobes, similarly to their presence in S. torazame, but in the intermediate lobe the immunoreactivity was confined to the peripheral cell cord closely adjacent to the neural lobe. The present findings are the first as regards the occurrence of alpha-MSH-like immunoreactivity in the glial system of the central nervous system of vertebrates and suggest diversity of expression and/or processing of proopiomelanocortin in the brain of elasmobranchs.