Evidence that N-acetylation regulates the behavioral activity of alpha-MSH in the rat and human central nervous system.

alpha-MSH immunoreactive peptides were fractionated and characterized in rat and human brain and rat pituitary by reversed phase high pressure liquid chromatographic techniques. alpha-MSH and deacetylated alpha-MSH were two major naturally existing peptides in both brain and pituitary gland. Subsequent experiments examined the roles of these two peptides in neuronal function. The alpha-MSH was clearly more effective than deacetylated alpha-MSH in improving performance on a visual discrimination task after intraperitoneal administration and in inducing excessive grooming after intraventricular administration. The difference in behavioral potency may be explained by the fact that alpha-MSH was much more resistant to peptidase degradation than was deacetylated alpha-MSH. N-acetylation of alpha-MSH may be an effective regulatory process for modulating the behavioral potency of the secretory product of alpha-MSH-containing pituitary cells and neurons.