Coexistence of melanin-concentrating hormone (MCH) and alpha-melanocyte-stimulating hormone (alpha-MSH) in the preoptic nucleus of the frog brain

Neuroanatomical distribution of MCH in the brain and pituitary of submammalian vertebrates

Melanin-concentrating hormone (MCH) is a cyclic neuropeptide that has been initially characterized from a salmon pituitary extract and subsequently identified in various species from all classes of vertebrates. The present review summarizes the current knowledge regarding the neuroanatomical distribution of MCH-immunoreactive neurons in submammalian vertebrates. In all species examined, MCH-immunoreactive perikarya are confined to the hypothalamus, with the exception of the cyclostome Lampetra fluvialis and the lungfish Protopterus annectens, in which additional populations of MCH-immunoreactive cell bodies occur in the telencephalon, and the frogs Rana ridibunda and Rana esculenta which exhibit MCH-positive perikarya in thalamic nuclei. In teleosts, in the frog R. ridibunda and in the L. fluvialis, MCH is present in the classical hypothalamic-neurohypophysial system indicating that the peptide may play the role of a neurohormone. In other groups, MCH-immunoreactive nerve fibers are widely distributed in various brain regions suggesting that, in these species, MCH in the central nervous system may act as a neurotransmitter or/and a neuromodulator rather than a neurohormone.

Neurosteroid biosynthesis: enzymatic pathways and neuroendocrine regulation by neurotransmitters and neuropeptides

Neuroactive steroids synthesized in neuronal tissue, referred to as neurosteroids, are implicated in proliferation, differentiation, activity and survival of nerve cells. Neurosteroids are also involved in the control of a number of behavioral, neuroendocrine and metabolic processes such as regulation of food intake, locomotor activity, sexual activity, aggressiveness, anxiety, depression, body temperature and blood pressure. In this article, we summarize the current knowledge regarding the existence, neuroanatomical distribution and biological activity of the enzymes responsible for the biosynthesis of neurosteroids in the brain of vertebrates, and we review the neuronal mechanisms that control the activity of these enzymes. The observation that the activity of key steroidogenic enzymes is finely tuned by various neurotransmitters and neuropeptides strongly suggests that some of the central effects of these neuromodulators may be mediated via the regulation of neurosteroid production.

Feeding-induced changes of melanin-concentrating hormone (MCH)-like immunoreactivity in goldfish brain

Intracerebroventricular (ICV) injection of melanin-concentrating hormone (MCH) influences feeding behavior in the goldfish and exerts an anorexigenic action in goldfish brain, unlike its orexigenic action in mammals. Despite a growing body of knowledge concerning MCH function in mammals, the role of MCH in appetite has not yet been well studied in fish. The aim of the present study was to investigate the involvement of endogenous MCH in the feeding behavior of the goldfish. We examined the distribution of MCH-like immunoreactivity (MCH-LI) in the goldfish brain and the effect of feeding status upon this distribution. Neuronal cell bodies containing MCH-LI were localized specifically to four areas of the hypothalamus. Nerve fibers with MCH-LI were found mainly in the neurohypophysis, with a few in the telencephalon, mesencephalon, and diencephalon. The number of neuronal cell bodies containing MCH-LI in the dorsal area adjoining the lateral recess of the third ventricle in the posterior and inferior lobes of the hypothalamus showed a significant decrease in fasted fish compared with that in normally fed fish, although other areas showed no evident differences. We also administered an antiserum against fish MCH (anti-MCH serum) by ICV injection and examined its immuno-neutralizing effect on food intake by using an automatic monitoring system. Cumulative food intake was significantly increased by ICV injection of the anti-MCH serum. These results indicate that MCH potentially functions as an anorexigenic neuropeptide in the goldfish brain, and that the further study of the evolutionary background of the MCH system and its role in appetite is warranted.

Central administration of melanin-concentrating hormone (MCH) suppresses food intake, but not locomotor activity, in the goldfish, Carassius auratus

Melanin-concentrating hormone (MCH) is a hypothalamo-pituitary peptide, which was first identified in the salmon pituitary as a hormone affecting body color. Recently, MCH has been implicated in the regulation of feeding behavior and energy homeostasis in mammals. Despite a growing body of knowledge concerning MCH in mammals, however, there is little information about the effect of MCH on appetite and behavior in fish. The aim of the present study was to investigate the action of MCH on feeding behavior and spontaneous locomotor activity in the goldfish. We administered synthetic MCH by intracerebroventricular (ICV) injection and examined its effect on food intake and locomotor activity using an automatic monitoring system. Both types of synthetic MCH we employed, which are of fish and human origin, were effective in stimulating aggregation of melanin granules in the melanophores of goldfish scales. Cumulative food intake was significantly decreased by ICV injection of both MCHs in a dose-dependent manner. ICV injection of fish MCH at the same doses as those used for examination of food intake induced no marked changes in locomotor activity during the observation period. These results suggest that MCH influences feeding behavior, but not spontaneous locomotor activity, in the goldfish, and may exert an anorexigenic action in the goldfish brain, unlike its orexigenic action in mammals.

Pituitary adenylate cyclase-activating polypeptide and its receptors in amphibians

Pituitary adenylate cyclase-activating polypeptide (PACAP), a novel peptide of the secretin/glucagon/vasoactive intestinal polypeptide superfamily, has been initially characterized in mammals in 1989 and, only 2 years later, its counterpart has been isolated in amphibians. A number of studies conducted in the frog Rana ridibunda have demonstrated that PACAP is widely distributed in the central nervous system (particularly in the hypothalamus and the median eminence) and in peripheral organs including the adrenal gland. The cDNAs encoding the PACAP precursor and 3 types of PACAP receptors have been cloned in amphibians and their distribution has been determined by in situ hybridization histochemistry. Ontogenetic studies have revealed that PACAP is expressed early in the brain of tadpoles, soon after hatching. In the frog Rana ridibunda, PACAP exerts a large array of biological effects in the brain, pituitary, adrenal gland, and ovary, suggesting that, in amphibians as in mammals, PACAP may act as neurotrophic factor, a neurotransmitter and a neurohormone.

Distribution of neuronal melanocortins in the spadefoot toad Spea multiplicata and effects of stress

We examined the effects of an acute stressor on regional alpha-melanocyte-stimulating hormone (alphaMSH) content in the New Mexican spadefoot toad, Spea multiplicata. We first used immunocytochemistry along with radioimmunoassay (RIA) to examine the distribution of pro-opiomelanocortin (POMC) neurons in the brain of Spea. Neurons immunoreactive for alphaMSH, beta-endorphin, and corticotropin were observed in the preoptic nucleus and ventral infundibulum of the hypothalamus. Ascending immunoreactive fibers projected to the olfactory nucleus, nucleus accumbens, and striatum. Numerous immunoreactive fibers were also observed in the hypothalamus. The thalamus/hypothalamus (T/HT) contained the greatest concentrations of alphaMSH as determined by RIA followed by the preoptic area (PO). Levels in the telencephalon, brain stem, and optic tectum (OT) were 14-23 times lower than in the T/HT. Exposure to a brief stressor elevated alphaMSH levels in the PO and OT. We conclude that Spea possesses two distinct POMC neuronal cell groups, one located in the anterior preoptic area and one located in the ventral infundibulum. Ascending projections to the basal ganglia might play an indirect role in tectal regulation and the control of prey-catching behavior. Exposure to an acute stressor alters brain alphaMSH content in Spea, although there are regional and temporal differences in the response pattern compared to Bufo. These findings are consistent with the notion that neuronal melanocortins influence how frogs and toads gather information about their environment during stress.

Differentiating ability of the pars intermedia in hypothalectomized frog tadpoles

It is generally accepted that hypothalectomy of frog tadpoles at the open neurula stage results in failure of the pars intermedia to develop. A pale body color is assumed to be evidence that the hypothalamus was completely removed. The present study, however, shows that hypothalectomized Rana japonica can develop into either albino, as already reported, or darkly pigmented tadpoles. In order to determine the extent to which the intermediate lobe can develop in these hypothalectomized tadpoles, their adenohypophyses were examined immunohistochemically by using anti-alphaMSH (melanocyte-stimulating hormone). In all the dark-colored larvae a pars intermedia had formed, though its size was very small. In the pale-colored tadpoles, on the other hand, the pars intermedia frequently failed to differentiate, but it was observed in 4 of 13 hypothalectomized larvae. In view of other investigators' data showing the complete absence of ACTH (adrenocorticotropin) cells in hypothalectomized tadpoles, hypophyses were also stained with anti-ACTH. Immunoreactive ACTH cells were detected in hypothalectomized tadpoles irrespective of the body pigmentation, although their incidence was lower than in normal controls. These data indicate that contact between the infundibulum and adenohypophysis is not absolutely essential for differentiation of MSH and ACTH cells in the frog.

Melanin-concentrating hormone system in the brain of the lungfish Protopterus annectens

The neurochemical anatomy of the lungfish brain is of particular interest, because many features in these animals might be representative of the common ancestor of land vertebrates. In the present study, we have investigated the localization and biochemical characteristics of melanin-concentrating hormone (MCH)-immunoreactive material in the central nervous system of the African lungfish, Protopterus annectens. The most prominent group of MCH-immunoreactive cell bodies was found in the dorsal hypothalamus. Additional groups of MCH-immunoreactive perikarya were detected in the telencephalon within the medial and dorsal pallium, the medial subpallium, and the ventral part of the lateral subpallium. Brightly immunofluorescent nerve fibers were seen in the anterior olfactory nucleus, the ventral part of the medial pallium, the medial subpallium, and the anterior preoptic area. In the diencephalon, the hypothalamus and the medial region of the dorsal thalamus exhibited a dense accumulation of fibers. MCH-immunoreactive fibers were also found in the tectum and the tegmentum of the mesencephalon and within the reticular formation of the rhombencephalon. In the pituitary, several small groups of cells of the intermediate lobe showed a bright fluorescence. Reversed-phase high-performance liquid chromatography (HPLC) analysis of diencephalon and pituitary extracts resolved a major MCH-immunoreactive peak that coeluted with synthetic salmon MCH. The distribution of MCH in the brain of P. annectens suggests that, in lungfishes, this peptide may exert neuromodulator or neurotransmitter functions. The presence of MCH-like immunoreactivity in the intermediate lobe of the pituitary indicates that, in dipnoans, MCH may also act as a typical pituitary hormone.

Distribution of neuromedin U-like immunoreactivity in the central nervous system of Rana esculenta

The distribution of perikarya and nerve fibers containing neuromedin U-like immunoreactivity in the brain of Rana esculenta was determined with an antiserum directed toward the carboxyl terminus of the peptide. In the telencephalon, immunoreactive perikarya were found in the olfactory bulb, the medial septum, and the diagonal band. In the diencephalon, labeled perikarya were detected in the anterior and posterior preoptic areas, the dorsal nucleus of the hypothalamus, the caudal part of the infundibulum, and the posterior tuberculum. In the mesencephalon, immunoreactive cell bodies were found only in the laminar nucleus of the torus semicircularis and the anterodorsal tegmental nucleus. In the rhombencephalon, labeled perikarya were detected in the secondary visceral nucleus, the cerebellar nucleus, the central gray, and the nucleus of the solitary tract. Immunoreactive nerve fibers were observed in all areas of the brain that contained labeled perikarya. The densest accumulations were found in the nucleus accumbens; the dorsal part of the lateral septum; the periventricular region of the ventral thalamus; the lateral part of the infundibulum; the anterodorsal, anteroventral, posterodorsal, and posteroventral tegmental nuclei; and the periaqueductal region of the tegmentum. The distribution of neuromedin U-like immunoreactivity in the frog brain was substantially different from the distribution described for the rodent brain.

Melanotropic peptides in the mammalian brain: the melanin-concentrating hormone

Melanin-concentrating hormone (MCH) has been identified in neurons of the mammalian brain. This review summarizes some current information regarding the cell biology of this neuropeptide and the topography of MCH-immunoreactive (-IR) neurons in several species including mouse, rat, hamster, guinea pig, rabbit, dog and monkey; and atlas of MCH-IR neurons in the hypothalamus and subthalamus of the brain of guinea pig is presented. Based upon the location of this MCH cell group, it is hypothesized that they may be functionally involved in circuits of extrapyramidal motor systems from striatal centers to the thalamus and cerebral cortex and to the midbrain and spinal cord.

Frog prohormone convertase PC2 mRNA has a mammalian-like expression pattern in the central nervous system and is colocalized with a subset of thyrotropin-releasing hormone-expressing neurons

The prohormone convertase (PC2) is expressed in the mammalian central nervous system (CNS) and has been shown to play an important role in the processing of certain neuropeptide precursors and prohormones at paired basic residues. Amphibian PC2 cDNA was recently cloned for the frog Xenopus laevis, and both its sequence and its pituitary expression pattern were shown to be very similar to those of mammalian PC2. To investigate further the function of PC2 in the vertebrate CNS, we used in situ hybridization histochemistry to localize the distribution of cells expressing PC2 mRNA in the frog brain and the spinal cord. The distribution of PC2-expressing cells was also compared with that of cells expressing thyrotropin-releasing hormone (TRH) mRNA or peptide. PC2-expressing cells were detected in specific nuclei that were widely distributed in the frog CNS. In forebrain, telencephalic PC2 mRNA was found in the olfactory bulb, pallium, striatum, amygdala, and septum, and diencephalic PC2 mRNA was seen in the preoptic area, thalamus, and hypothalamus. More posteriorly, PC2 cells were localized to midbrain tegmentum, the torus semicircularis, and the optic tectum, as well as the cerebellum, brainstem, and spinal cord. Despite this wide distribution steady-state levels of PC2 mRNA were clearly different in various brain nuclei. Regions with higher levels showed good correspondence to areas shown by others in frog to contain large numbers of neuropeptide-expressing cells, including TRH cells. On the other hand, not all brain areas with high levels of TRH mRNA had high levels of PC2 mRNA. Localization studies combining in situ hybridization and immunocytochemistry showed that, at least in optic tectum and brainstem, PC2 mRNA and pro-TRH peptide coexist. These findings suggest that pro-TRH is processed by PC2 in some, but possibly not all, brain regions. Thus, different converting enzymes may be involved in pro-TRH processing in different brain regions.

Immunohistochemical distribution and biological activity of pituitary adenylate cyclase-activating polypeptide (PACAP) in the central nervous system of the frog Rana ridibunda

The primary structure of frog pituitary adenylate cyclase-activating polypeptide (PACAP) has recently been determined and the results show that the sequence of PACAP has been highly conserved during evolution. In particular, the structure of the 1-27 fragment of PACAP is identical in frog and mammals. Using an antiserum raised against PACAP27, we have investigated the distribution of PACAP-containing neurons in the central nervous system of the frog Rana ridibunda by the immunofluorescence technique. The main populations of immunoreactive perikarya were located in the medial and ventral diencephalon, i.e., the preoptic nucleus, the ventral and dorsal infundibular nuclei, the nucleus posterocentralis thalami, and the ventral and ventrolateral areas of the thalamus. In the telencephalon, sparse cell bodies were found in the nucleus accumbens septi, the amygdala, the pallial commissure, and the bed nucleus of the pallial commissure. In the hindbrain, the torus semicircularis, the nucleus profundus and the nucleus anteroventralis tegmenti of the mesencephalon also contained populations of PACAP-immunoreactive perikarya. Beaded nerve fibers were observed throughout the brain. Occasionally they formed bundles, e.g., from the ventral infundibulum to the external vascular layer of the median eminence, from the central thalamus to the optic tectum, and rostrocaudally, from the nucleus accumbens septi to the nucleus entopeduncularis. Other areas, such as the interpeduncular nucleus, the nucleus isthmi and the roots of cranial nerves V and VIII in the medulla oblongata, were also densely innervated. The adenylate cyclase-stimulating activity of PACAP was tested by using a static incubation technique for hypothalamic slices.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzymological studies of melanin concentrating hormone (MCH) and related analogues

1. Salmon melanin concentrating hormone (MCH) is a cyclic heptadecapeptide possessing the following primary structure: Asp-Thr-Met-Arg-Cys-Met-Val-Gly-Arg-Val-Tyr-Arg-Pro-Cys-Trp-Glu-Val. 2. In the fish, Synbranchus marmoratus, skin bioassay MCH5-15 is equipotent to MCH whereas MCH5-14, which comprises only the ring structure, is about 100-fold less active. 3. MCH and two fragment analogues, MCH5-15 and MCH5-14, were studied to determine their relative stability in the presence of fish serum and purified proteolytic enzymes, trypsin and alpha-chymotrypsin. 4. After 4 hr incubation in fish serum, MCH5-15 retained 1/100, MCH5-14 1/1000 and MCH only 6/1000 of the potency of the native hormone. 5. The three peptides were also very resistant to degradation by purified proteolytic enzymes involving the following relative order of resistance: MCH5-14 > MCH5-15 > MCH. MCH5-14 potency was not altered after a 1 hr incubation in either enzyme whereas MCH retained 1/10 and 4/100 of its original potency, and MCH5-15 retained 1/10 and 8/10 of its original potency, after 1 hr in trypsin and alpha-chymotrypsin, respectively.

Immunohistochemical localization of delta sleep-inducing peptide-like immunoreactivity in the central nervous system and pituitary of the frog Rana ridibunda

The purpose of the present study was to investigate the distribution of delta sleep-inducing peptide in the brain and pituitary of the frog Rana ridibunda and to determine the possible effect of this nonapeptide on adrenocorticotropic hormone and corticosteroid secretion. Delta sleep-inducing peptide-like immunoreactive fibres were observed throughout the brain of the frog. These fibres generally exhibited the characteristics of glial cell processes. Scarce delta sleep-inducing peptide-positive fibres were seen in the olfactory bulb and in the periventricular areas of the telencephalon. In the diencephalon, numerous delta sleep-inducing peptide-containing processes were noted in the preoptic nucleus, the infundibular nuclei and the median eminence. A few cerebrospinal fluid-contacting cells were visualized in the ventral nucleus of the infundibulum. Delta sleep-inducing peptide-positive fibres were also observed in the mesencephalon, radiating through the different layers of the tectum. In the cerebellum, all Purkinje cells exhibited delta sleep-inducing peptide-like immunoreactivity. More caudally, numerous delta sleep-inducing peptide-positive fibres were noted in the vestibular nucleus of the rhombencephalon. A dense network of delta sleep-inducing peptide-containing fibres was seen in the pars nervosa of the pituitary. In the distal lobe, a population of endocrine cells located in the anteroventral region contained delta sleep-inducing peptide-immunoreactive material. Labelling of consecutive sections of the pituitary by delta sleep-inducing peptide and adrenocorticotropic hormone antiserum revealed that a delta sleep-inducing peptide-related peptide is expressed in corticotroph cells. The possible role of delta sleep-inducing peptide in the control of adrenocorticotropic hormone and corticosteroid release was studied in vitro, using the perifusion system technique. Administration of graded doses of delta sleep-inducing peptide (from 10(-8) to 10(-6) M) to perifused frog anterior pituitary cells did not affect the spontaneous release of adrenocorticotropic hormone. In addition, prolonged infusion of delta sleep-inducing peptide (10(-6) M) did not alter the stimulatory effect of corticotropin-releasing factor (10(-7) M) on adrenocorticotropic hormone secretion. Similarly, exposure of frog interrenal slices to delta sleep-inducing peptide did not induce any modification of spontaneous or adrenocorticotropic hormone-evoked secretion of corticosterone and aldosterone. Our results provide the first evidence for the presence of a delta sleep-inducing peptide-related peptide in lower vertebrates. The occurrence of delta sleep-inducing peptide-like immunoreactivity in specific areas of the brain suggests that the peptide may act as a neuromodulator.(ABSTRACT TRUNCATED AT 400 WORDS)

Nucleotide sequence and tissue-specific expression of the rat melanin concentrating hormone gene

Melanin concentrating hormone (MCH) is a key neuroendocrine peptide which is involved in the regulation of body color in teleost fish. Antigenically similar peptides exist in higher vertebrates including rodents and man. The precise function(s) of these peptides in these higher vertebrates has yet to be fully elucidated, although regulatory roles in stress-induced or corticotropin-releasing hormone-stimulated ACTH release and/or water balance have been proposed. The salmon, rat, and human MCH cDNA clones have been isolated and sequenced. We isolated and characterized the structure of the rat MCH gene. In addition to providing the complete nucleotide sequence of this gene, we demonstrate that there is a single copy of this gene in the rat genome. The structure of the rat MCH gene indicates that the MCH mRNA is encoded by three exons. Using primer extension and RNase protection assays, the transcriptional start sites of hypothalamic MCH mRNA were determined, allowing us to define the promoter region of this gene. We also characterize the central nervous system distribution of expression of the MCH gene by Northern blot analysis, demonstrating that the MCH mRNA is found predominantly if not exclusively within the hypothalamus.

Structures of two genes coding for melanin-concentrating hormone of chum salmon

Two MCH genes coding for melanin-concentrating hormone (MCH) were isolated from a chum salmon liver DNA library and characterized. They were shown to be intronless genes with 0.63-kb exons, each of which commonly consisted of an about 80-bp 5'-untranslated region, a region coding for 132 amino acids (aa) MCH precursor protein and an approx. 160-bp 3'-untranslated region. About 20 bp upstream from the putative cap site, sequences were found corresponding to the TATA box. The two genes were 86% identical at the nucleotide sequence level. Sequences homologous to the chum salmon MCH genes were present in the genomes of other fish such as catfish, carp and Chinese grass carp, whereas no highly homologous sequence could be detected in other vertebrate genomes.

Two precursors of melanin-concentrating hormone: DNA sequence analysis and in situ immunochemical localization

Two precursors to Chinook salmon (Oncorhynchus tshawytscha) melanin-concentrating hormone, an important factor in teleosts involved in the control of skin pigmentation and stress responsiveness, have been identified from DNA sequence analysis. Both precursors encode proteins of 132 amino acids and they share 107/132 amino acid identities. The biologically active 17-residue peptide is located at the C terminus of both precursors and can be liberated by proteolytic cleavage following two adjacent arginine residues. Additional putative proteolytic processing sites are located within the two precursors. Northern analysis demonstrated an intense hybridization signal of 750 nucleotides in the hypothalamus. Immunocytochemical studies as well as in situ hybridization analyses identify intensely staining cell bodies in the hypothalamus in the area of the lateral tuberal nucleus.

Immunocytochemical demonstration of melanin-concentrating hormone and proopiomelanocortin-like products in the brain of the trout and carp

Immunocytochemistry on frozen sections revealed that in both the trout and the carp, parvocellular neurones located in the medial basal hypothalamus (medial nucleus lateralis tuberis) were immunostained by antisera against three molecules known to be derived from the proopiomelanocortin (POMC) molecule, viz: alpha-melanocyte-stimulating hormone (alpha MSH), ACTH, and salmonid NPP--the whole N-terminal sequence preceding ACTH in the POMC precursor. Axons from these neurones extended into various regions of the brain but did not appear to project into the pituitary gland. Antiserum against salmonid melanin-concentrating hormone (MCH) immunostained magnocellular neurones in the lateral basal hypothalamus (lateral nucleus lateralis tuberis). Axons from some of these neurones projected into the brain while other axons extended into the pituitary gland. In the carp, but not in the trout, some MCH neurones were also immunostained by antisera against alpha MSH but not by antisera against the other POMC molecules.

Melanin-concentrating hormone (MCH) immunoreactivity in the brain and pituitary of the dogfish Scyliorhinus canicula. Colocalization with alpha-melanocyte-stimulating hormone (alpha-MSH) in hypothalamic neurons

The distribution of melanin-concentrating hormone (MCH) in the central nervous system of the dogfish Scyliorhinus canicula was determined by indirect immunofluorescence and peroxidase-anti-peroxidase techniques, using an antiserum raised against synthetic salmon MCH. Three groups of MCH-positive cell bodies were localized in the posterior hypothalamus. The most prominent cell group was detected in the nucleus sacci vasculosi. Scattered MCH-immunoreactive cells were observed in the nucleus tuberculi posterioris and in the nucleus lateralis tuberis. At the pituitary level, the caudal part of the median lobe of the pars distalis contained strongly MCH-positive perikarya. Some of these cells were liquor-contacting-type. Immunoreactive fibers originating from the hypothalamic perikarya projected throughout the dorsal wall of the posterior hypothalamus. Positive fibers were also detected within the thalamus and the central gray of the mesencephalon. The distribution of MCH-containing neurons was compared to that of alpha-MSH-immunoreactive elements using consecutive, 5-micron thick sections. Both MCH- and alpha-MSH-immunoreactive peptides were found in the same neurons of the nucleus sacci vasculosi. These data suggest that MCH and alpha-MSH, two neuropeptides which exert antagonistic activities on skin melanophores, may also act in a coordinate manner in the central nervous system of cartilaginous fish.

Melanin concentrating hormone. II. Structure and biosynthesis of melanin-concentrating hormone

Melanin-concentrating hormone is a neuropeptide produced in teleost hypothalami and transferred to the neurohypophysis. Salmon MCH was a novel cyclic heptadecapeptide capable of inducing melanin aggregation of integumentary melanophores at picoto nano-molar concentrations in all teleosts tested. The MCH gene is intronless and the exon encodes a 132 amino acid precursor protein, in which the heptadecapeptide of MCH locates at the C-terminal end. Immunohistochemical surveys with anti-salmon MCH antiserum strongly suggest that an MCH-like peptide is present in the hypothalami of higher vertebrates. Biological effects of salmon MCH on other vertebrates are found to be versatile.

Characterization of metorphamide-like immunoreactivity in the zona incerta and lateral hypothalamus: co-localization with alpha-melanocyte-stimulating hormone-like immunoreactivity

Double-staining in either vibratome or paraffin sections using contrasting chromogens revealed an alpha-melanocyte-stimulating hormone (alpha-MSH)-containing cell group in the arcuate nucleus, a metorphamide-containing cell group in the paraventricular hypothalamus, and an extensive group of magnocellular perikarya in the zona incerta (ZI) and the lateral hypothalamus (LH) that appeared to contain both antigens. Staining of adjacent paraffin sections also suggested that most (and perhaps all) of the magnocellular perikarya in the ZI and LH that contained metorphamide-like immunoreactivity also contained alpha-MSH-like immunoreactivity. Metorphamide-like immunoreactivity in the ZI and the LH was abolished by absorption of the antiserum with metorphamide but was unaffected by absorption with alpha-MSH. alpha-MSH-like immunoreactivity in the ZI and LH was abolished by absorption of the antiserum with alpha-MSH but was unaffected by absorption with metorphamide. Antisera directed against [Met5]-enkephalin (Met-ENK), [Met5]-enkephalin-Arg6,Gly7,Leu8 (ENK-8), [Met5]-enkephalin-Arg6,Phe7 (ENK-7), neuropeptide Y, and FMRF-amide did not stain magnocellular perikarya in the ZI and LH. Pretreatment of paraffin sections with trypsin resulted in the appearance of [Met5]-enkephalin-Arg6-like immunoreactivity in the ZI and LH. Pretreatment of paraffin sections with trypsin did not reveal any occult Met-ENK-, ENK-7- or ENK-8-like immunoreactivity in either the ZI or the LH. These observations indicate that magnocellular neurons in the ZI and LH contain both a metorphamide-like and an alpha-MSH-like peptide but do not express either the preproenkephalin or the prepro-opiomelanocortin48 gene.

Coexistence of melanin-concentrating hormone and alpha-melanocyte-stimulating hormone immunoreactivities in the central nervous system of the locust, Locusta migratoria

The distribution of melanin concentrating hormone (MCH) in the central nervous system of the locust Locusta migratoria was studied by the indirect immunofluorescence technique, using antibodies against salmon MCH. Most MCH-immunoreactive perikarya were found in the optic lobes at both sides of the brain, dorsally with respect to the lamina ganglionaris. The same neurons also contain alpha-melanocyte-stimulating hormone (alpha-MSH)-like material. In addition, a moderate number of MCH-like neurons, which were devoid of alpha-MSH-immunoreactive substances, was observed in the pars intercerebralis. Bright immunofluorescent fibers were visualized in various regions of the central nervous system of the locust: the optic lobes, the ocelli, the proto-and deuterocerebrum, the subesophageal connectives and the corpora cardiaca. In the ventral nerve cord and the subesophageal ganglion, where alpha-MSH-like cell bodies were encountered, MCH immunoreactive perikarya were absent and immunoreactive fibers were scarce. The coexistence of MCH and alpha-MSH-immunoreactive material within the same specific neurons might indicate an evolutionary relationship of both peptides.