Melanin-concentrating hormone (MCH) is a 19 amino acid cyclic neuropeptide,which is mainly expressed in the hypothalamus. MCH modulates feeding behavior, aggression, anxiety, arousal and reproductive function in mammals by controlling the release of luteinizing hormone (LH). The melanin-concentrating hormone receptor (MCHR, also designated SLC-1) is a glycosylated G-protein coupled receptor that migrates between 45-50 kDa on SDS-PAGE. MCHR mediates the effects of MCH through Gai and/or Gaq signaling and is expressed in several regions of the brain, including the cerebral cortex, amygdala, thalamus and hypothalamus. MCH and MCHR have also been implicated in stimulating leptin expression and secretion in adipocytes, which suggests that the melanin-concentrating hormone and its receptor may be potential targets for modulating obesity.