Psychopharmacological and endocrinological effects of melanocyte stimulating hormones in normal man.

Abstract

A double blind crossover trial of the effects of synthetic alpha melanocyte stimulating hormone (alpha MSH) and synthetic beta melanocyte stimulating hormone (beta 1–22 MSH) on the contingent negative variation (CNV), performance (mental arithmetic; verbal and visual memory), and mood (selfrating scale) was carried out on four normal male subjects. All subjects received three 10-min infusions in random order at weekly intervals (10 ml diluent alone, 10 mg alpha MSH or 10 mg beta 1–22 MSH, both in 10 ml acid saline) and were observed for 1 h after the infusion and again 24 h later. Plasma concentrations of alpha and beta MSH, thyrotrophin, growth hormone, gastrin, cortisol, calcium, cholesterol, and triglycerides were measured before and after the infusions in addition to the CNV and mental performance tests. Plasma half-lives were found to be 20.8 min for alpha MSH and 15.1 min for beta MSH. The infusions had little effect on most measures, but after alpha MSH there was a significant improvement in verbal memory, and in two subjects there was a significant rise in plasma growth hormone without a rise in plasma cortisol. After beta 1–22 MSH there was a significant decline in verbal memory in all four subjects. These results lend support to the accumulating evidence that peptides similar to the melanocyte stimulating hormones have a neuroendocrine effect in man. Infusion of melanocyte stimulating hormone inhibiting factor (MIF; 10 mg in 10 ml normal saline given over 2 min) in six other subjects caused no change in CNV magnitude, reaction time, heart rate, or serum beta MSH level compared to control saline infusion.