Effects of cholecystokinin-like peptides on rearing activity and hexobarbital-induced sleep.

Caerulein and the C-terminal octapeptide of cholecystokinin (CCK-8), when subcutaneously injected into mice, inhibited spontaneous rearing activity and prolonged the hexobarbotal sleeping time. These effects were resistant to naloxone. In molar terms, caerulein was 40 times (hexobarbital potentiation) or 115 times (rearing) more potent than diazepam. CCK-8 was less active than caerulein) though still superior to diazepam.