Effects of prolactin-releasing peptide (PrRP) on sleep regulation in rats.

The present study examined in rats how prolactin-releasing peptide (PrRP), a new hypothalamic hormone, infused centrally during the dark period affects sleep and plasma levels of prolactin (PRL). At a dose of 0.1 nmol, PrRP increased only rapid eye movement (REM) sleep, whereas with 1.0 nmol both non-REM sleep and REM sleep were enhanced. However, 10.0 nmol of PrRP increased only non-REM sleep with a febrile response. The levels of plasma PRL were elevated during the infusion of PrRP with 0.1 and 1.0 nmol. Consequently, the increased release of PRL correlated with significant increases in REM sleep, but not in non-REM sleep.