Melanin-concentrating hormone-like immunoreactive substance in the rat hypothalamus.

点击翻译按钮获取中文摘要

Melanin-concentrating hormone (MCH) is a neuropeptide synthesized in the teleost hypothalamus and stimulates melanin aggregation within teleost melanophores. In the rat brain, however, MCH-bioactivity and immunoreactivity have been reported independently.In the present project, we characterized MCH-like substance in the rat brain by both an in vitro fish-scale melanophore-bioassay and a radioimmunoassay (RIA) with an antiserum against salmon MCH. Futhermore, subcellular localization of the MCH in the rat brain was examined by immunocytochemistry using electron microscopy. 1. Structure-activity relationships of the salmon MCH molecule were confirmed. MCH-bioactivity requires the disulfide bonding between cystein and amino acid residues (Tyr^<11> and Arg^<12>). Salmon MCH antiserum used in our studies is directed towards the carboxy-terminus and requires the cyclic configuration for recognition. 2. MCH-immunoreactivity and -bioactivity were present together in the same effluent fractions of the rat hypothalamic extract by reverse-phase high-performance liquid chromatography (HPLC). 3. MCH-immunoreactive cell bodies in the rat brain were confined to the hypothalamus. At electron microscopic level, MCH-immunoreactivity was located specifically in secretory granules in MCH-positive neurons and their processes. 4. Coexistence of immunoreactivity for MCH and -MSH was presented in the hypothalamus of the rat.Our results strongly upport the notion that rat MCH-like substance may be homologous but not identical to salmon MCH, and may serve some neurotransmitter and/or neuromodulator role in the brain of the rat.