Melanin-concentrating hormone (MCH) is a cyclic peptide, isolated and sequenced originally from salmon pituitary. The rat MCH is 19 amino acids long, two amino acids longer than its salmon counterpart, and is identical to the human MCH, the sequence of which was deduced by cloning.  In rodents, MCH is prominently expressed in the perikarya of the lateral hypothalamus and the zona incerta, and projects broadly throughout the central nervous system(CNS). MCHR exhibits several different structures. First, under its original name of somatostatin-like receptor (SLC)-1 or GPR24, it has been described as a 402 amino acid-long human GPCR that was discovered by genomic cloning and delineated by an assigned start codon. In addition to the SLC-1 form of the MCHR, two other MCHR cDNAs were found in a human embryonic brain cDNA library. MCH may function as a neurotransmitter/neuromodulator in a broad array of behavioral responses. MCHR receptor is in fact SLC-1, an orphan G-protein-coupled receptor (GPCR). The SLC-1 GPCR was discovered as an expressed sequence tag exhibiting about 40% homology in its hydrophobic domains to the five somatostatin receptors.SLC-1 reactivity was monitored in three different ways: (1) by intracellular changes in calcium influxes upon coexpression of a Gaq/i3 chimeric protein engineered to force SLC-1 coupling to the phospholipase C pathway; (2) by inhibition of intracellular cAMP accumulation; and (3) by G-protein-gated inwardly rectifying potassium channels (GIRKs) in Xenopus oocytes injected with SLC-1 cRNAs.


1.Saito Y, et al. Trends Endocrinol Metab. 2000;11(8):299–303.