The effects of caerulein on nocturnal sleep

Caerulein, a decapeptide chemically related to cholecystokinin octapeptide, was examined polysomnographically for its effect on nocturnal sleep in healthy volunteers. The subjects were 6 males (20-24 years of age). Either a placebo (saline) or caerulein 0.6 microgram/kg was administered intramuscularly to volunteers at 23:00. Polysomnograms were then recorded from 23:00 till 06:30. Little variation in sleep period time, total sleep time, sleep efficiency index, sleep latency, or REM sleep latency in the drug night were found as compared to the control night values. The percentage of REM stage sleep increased significantly (P less than 0.01) on the drug administered night, whereas the change in the percentages of each of the other stages was not significant. The REM density of the vertical eye movements tended to increase on the drug night, but the density of the horizontal eye movements showed no change. There were no changes in the spontaneous GSRs in either vola or dorsum manus. As caerulein shows alpha-1 adrenergic receptor blocker activity, it is suggested that caerulein may increase REM sleep by affecting the central noradrenergic neurons.