Effect of prolactin on the sleep-wake cycle in the rat

The purpose of this study was to examine the effects of prolactin on the sleep-wake cycle. Ovine prolactin was injected subcutaneous at a dose of 10 micrograms/animal or intra-cerebro-ventricularly at doses of 100, 10 and 1 ng/animal. The subcutaneous injections were given during either the diurnal or nocturnal period. Results indicate that oPRL decreases paradoxical sleep duration when injected during the dark period and increases it when injected during the light period. The i.c.v. injections were given only during the dark period and the effects were similar to those obtained with the s.c. injections. There was no effect on slow-wave sleep duration irrespective of injection time or injection site.