Melanin-concentrating hormone system in the brain of the lungfishProtopterus annectens

Abstract

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.

Melanin-concentrating hormone system in the brain and skin of the cichlid fish Cichlasoma dimerus : anatomical localization, ontogeny and distribution in comparison to α-melanocyte-stimulating hormone-expressing cells

“…There is considerable evidence indicating the existence of a strong evolutionary pressure that acted to conserve the sequence of the biologically active domain of MCH (Vallarino et al 1998). It has been shown that rat and human MCH are identical (Nahon et al 1989;Vaughan et al 1989;Presse et al 1990).…”

“…Similarly, eel MCH and salmon MCH differ by only one substitution (Asn vs Asp) located outside the ring structure that corresponds to the biologically active domain of the peptide (Kawauchi et al 1983(Kawauchi et al , 1993. In the cyclic region of the molecule, mammalian and salmonid MCH exhibit only one conservative substitution (Leu vs Val) (Vallarino et al 1998). All these data and the absence of MCH immunoreactivity in the preadsorption tests (with rat MCH and salmon MCH) strongly suggest the specificity of rat MCH in recognizing Cichlasoma MCH not only in the brain and pituitary gland but also in skin neuromasts.…”

“…In the ayu, Plecoglossus altivelis, ACTH-and MSH-ir cells were detected on the hatching day (Saga et al 1999). Colocalization of MCH and αMSH has been reported in several vertebrate species: rat (Naito et al 1986;Fellman et al 1987;Pelletier et al 1987), frog, Rana ridibunda (Andersen et al 1987), dogfish, Scyliorhinus canicula (Vallarino et al 1989), and lungfish, Protopterus annectens (Vallarino et al 1998), but not in teleosts.…”

“…Although it acts as a neurohypophyseal hormone only in teleosts and possibly in holosteans (Sherbrooke and Hadley 1988), the peptide was found in the hypothalamus of all vertebrates examined to date. In the lungfish, Protopterus annectens (Sarcopterygii, Dipnoi), the presence of MCH-like immunoreactivity in the intermediate lobe of the pituitary indicates that in dipnoans MCH may act as a typical pituitary hormone (Vallarino et al 1998). In Actinopterygii, particularly, MCH acts as an adenohypophyseal regulator and, except in Polypteriformes, as a neurohypophyseal hormone as well (Baker and Bird 2002).…”

Immunolocalization of Two Putative Pigmentotropins Akh I and -MSH-Like Immunoreactivities in the Brain of Rough Woodlouse, Porcellio Scaber and Pill Bugs Armadillidium Vulgare (Crustacea, Isopoda).

“…Since then, the biological effect of MSH on skin pigmentation was studied extensively in vertebrates (Bunel et al, 1992;Vallarino et al, 1998;Jegou et al, 1993). Colocalization of α-MSH and MCH has been reported in the dorsolateral hypothalamic region of the rat (Naito et al, 1986;Fellman et al, 1987), in the preoptic nucleus of the frog, Rana ridibunda (Andersen et al, 1987), and in the nucleus sacci vasculosi in the brain of the dogfish, Scyliorhinus canicula (Vallarino et al, 1989) and lungfish, Protopterus annectens (Vallarino et al, 1998) and cichlid fish Cichlasoma dimerus (Pandolfi et al, 2003).…”