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

黑素浓缩激素(MCH)是一种在硬骨下丘脑合成的神经肽，能刺激硬骨黑素载体内的黑色素聚集。然而，在大鼠脑中，MCH生物活性和免疫反应性是独立报道的。在本项目中，我们通过体外鱼鳞黑素载体生物分析和使用鲑鱼MCH抗血清的放射免疫分析(RIA)来表征大鼠脑中的MCH样物质。此外，用免疫细胞化学和电子显微镜观察了MCH在大鼠脑内的亚细胞定位。1.确定了鲑鱼MCH分子的构效关系。MCH的生物活性需要半胱氨酸和氨基酸残基(Tyr^&lt；11&gt；和Arg^&lt；12&gt；)之间的二硫键。我们研究中使用的鲑鱼MCH抗血清是针对羧基末端的，需要环状构型才能识别。2.大鼠下丘脑提取液中MCH免疫反应和生物活性同时存在于大鼠下丘脑提取液的同一流出部位。3.大鼠脑内MCH免疫反应阳性胞体局限于下丘脑。在电子显微镜水平上，MCH阳性神经元及其突起的分泌颗粒中有特异性的表达。4.在大鼠下丘脑中存在MCH和-MSH的共存免疫反应。我们的结果有力地支持了大鼠MCH样物质可能与鲑鱼MCH同源但不完全相同的观点，并可能在大鼠脑内起神经递质和/或神经调节剂的作用。

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.