Influence of proopiomelanocortin-derived peptides on the sleep-waking cycle of the rat.

The effects of i.c.v. injections of different proopiomelanocortin-derived peptides were tested on the rat sleep-waking cycle: adrenocorticotropic hormone (ACTH) had no effect. In contrast, administration of two ACTH-derived peptides was followed by a selective and significant increase of each sleep state: desacetyl-alpha-melanocyte-stimulating hormone induced an increase of slow-wave sleep, while corticotropin-like intermediate lobe peptide was followed by an increase of paradoxical sleep. Both alpha-melanocyte-stimulating hormone in its acetylated form and alpha-endorphin were inactive.