alpha-melanocyte-stimulating hormone (alpha-MSH) and melanin-concentrating hormone (MCH) modify monoaminergic levels in the preoptic area of the rat

The effect of perfusion of melanin-concentrating hormone (MCH) or alpha-melanocyte-stimulating hormone (alpha-MSH) (100 ng/mu l) in the ventromedial nucleus (VMN) or medial preoptic area (MPOA) on monoaminergic levels of female rats was measured using microdialysis and HPLC-electrochemical detection. In the MPOA, alpha-MSH raised 5-HIAA concentration, whereas MCH reduced both 5-HT and 5-HIAA. Neither peptide had any effect in the VMN. The opposite effects of the peptides on the serotonergic system might be responsible for their antagonistic or opposite actions previously reported on several CNS functions. Dopamine may mediate the similar effects of the two peptides, because alpha-MSH inhibits dopaminergic release in the MPOA (but not VMN) and MCH tends to follow the same pattern. (C) 1997 Elsevier Science Inc.