Sleep-promoting activity of prolactin-releasing peptide (PrRP) in the rat.

The present study examines whether or not prolactin-releasing peptide (PrRP) infused intracerebroventricularly (i.c.v.) affects sleep and the release of prolactin (PRL) and growth hormone (GH) in rats. At a dose of 0.1 nmol, PrRP promoted rapid-eye-movement (REM) sleep, whereas 1.0 nmol increased both non-REM and REM sleep and 10.0 nmol enhanced only non-REM sleep. During the i.c.v. infusion of PrRP with 0.1 nmol, levels of plasma PRL were elevated, but GH levels were significantly decreased. Since it is reported that PrRP fails to induce PRL release from the male pituitary, the stimulatory effects of PrRP on PRL release observed here seem to be indirect. However, PRL stimulated by i.c.v.-infused PrRP could take part in the REM sleep-promoting activity of PrRP.