L-364,718, a cholecystokinin-A receptor antagonist, suppresses feeding-induced sleep in rats

Feeding induces increased sleep in several species, including rats. The aim of the study was to determine if CCK plays a role in sleep responses to fe eding. We induced excess eating in rats by 4 days of starvation and studied the sleep responses to refeeding in control and CCK-A receptor antagonist- treated animals. Sleep was recorded on 2 baseline days when food was provid ed ad libitum. After the starvation period, sleep was recorded on 2 refeedi ng days when the control rats (n = 8) were injected with vehicle and the ex perimental animals (n = 8) received intraperitoneal injections of L-364,718 (500 mug/kg, on both refeeding days). In the control group, refeeding caus ed increases in rapid eye movement sleep (REMS) and non-REMS (NREMS) and de creases in NREMS intensity as indicated by the slow-wave activity (SWA) of the electroencephalogram. CCK-A receptor antagonist treatment completely pr evented the SWA responses and delayed the NREMS responses to refeeding; REM S responses were not simply abolished, but the amount of REMS was below bas eline after the antagonist treatment. These results suggest that endogenous CCK, acting on CCK-A receptors, may play a key role in eliciting postprand ial sleep.