Cerebroventricular infusion of cholecystokinin (CCK-8) restores REM sleep in parachlorophenylalanine (PCPA)-pretreated cats.

Recently, some studies have shown that cholecystokinin (CCK-8) administered either intraventricularly or intraperitoneally has no effect on sleep. However, since in such studies CCK-8 was given at times when sleep predominates, in this study the effects of CCK-8 on sleep were determined in parachlorophenylalanine (PCPA) (400 mg/kg)-pretreated insomniac cats. Twenty-four hours after the second injection of PCPA one group of cats received 100 ng/100 microliter of CCK-8 and another group only 100 microliter of saline. A third group was studied only under the effects of PCPA. The results showed that CCK-8 was capable of restoring sleep in the otherwise insomniac cats and that this effect was restricted to REM sleep only. The observed REM sleep-promoting action of CCK-8 supports the notion that this polypeptide may be involved in REM sleep regulation.