Salmonid melanin-concentrating hormone inhibits corticotrophin release

Melanin-concentrating hormone (MCH) is a neural peptide associated with colour change in fishes. We show here that it also inhibits corticotrophin (ACTH) secretion. Synthetic salmonid MCH at a concentration of 100pmol/l reduced the in-vitro release of ACTH by pars distales (pDs) taken from stressed trout. At lower concentrations (10pmol/l) the peptide inhibited CRF-41-induced secretion of ACTH by pDs removed from unstressed trout, while at higher concentrations (10nmol/l) it reduced the corticotrophic response of rat pituitary tissue to CRF-41.