The somatostatin analogue SMS 201-995 promotes paradoxical sleep in aged rats

Sleep patterns were recorded in aged rats (800- to 840-day-old) under control conditions and following either intraperitoneal injections of three different doses of the octapeptide somatostatin analogue SMS 201-995 (SMS) or after spontaneous oral intake of SMS-containing water (0.003 mg/ml). The intraperitoneal administration of SMS resulted in a dose-dependent and selective increase of paradoxical sleep (PS). Similarly, the spontaneous oral ingestion of SMS induced a significant increase of the daily duration of PS. Slow wave sleep remained unchanged in both cases. These findings confirm previous results demonstrating a role of somatostatin in the generation of PS. In addition, they suggest that sleep deficits during aging may be the consequence of decreased age-related somatostatin release.