The distribution of the mRNA and protein products of the melanin-concentrating hormone (MCH) receptor gene, slc-1, in the central nervous system of the rat

Melanin-concentrating hormone (MCH), a 19 amino acid cyclic peptide, is lar gely expressed in the hypothalamus. It is implicated in the control of gene ral arousal and goal-orientated behaviours in mammals, and appears to be a key messenger in the regulation of food intake. An understanding of the bio logical actions of MCH has been so far hampered by the lack of information about its receptor(s) and their location in the brain. We recently identifi ed the orphan G-protein-coupled receptor SLC-1 as a receptor for the neurop eptide MCH. We used in situ hybridization histochemistry and immunohistoche mistry to determine the distribution of SLC-1 mRNA and its protein product in the rat brain and spinal cord. SLC-1 mRNA and protein were found to be w idely and strongly expressed throughout the brain. Immunoreactivity was obs erved in areas that largely overlapped with regions mapping positive for mR NA. SLC-1 signals were observed in the cerebral cortex, caudate-putamen, hi ppocampal formation, amygdala, hypothalamus and thalamus, as well as in var ious nuclei of the mesencephalon and rhombencephalon. The distribution of t he receptor mRNA and immunolabelling was in good general agreement with the previously reported distribution of MCH itself. Our data are consistent wi th the known biological effects of MCH in the brain, e.g. modulation of the stress response, sexual behaviour, anxiety, learning, seizure production, grooming and sensory gating, and with a role for SLC-1 in mediating these p hysiological actions.