SELECTIVE ACTIVATION OF CCK-B RECEPTORS DOES NOT INDUCE SLEEP AND DOES NOT AFFECT EEG SLOW-WAVE ACTIVITY AND BRAIN TEMPERATURE IN RATS

Systemic injections of cholecystokinin octapeptide sulfate ester (CCK- 8-SE) elicit various behavioral and autonomic responses, such as incre ases in nonrapid-eye-movement sleep (NREMS) and hypothermia. There are two CCK receptors; both CCK-A and CCK-B receptors are stimulated by C CK-8-SE. The relative importance of the CCK-A and CCK-B receptors in t he somnogenic and hypothermic effects of CCK-8-SE is not well understo od. In the present experiments, we studied the effects of the selectiv e activation of CCK-B receptors by CCK tetrapeptide (CCK-4) or nonsulf ated CCK-g (CCK-8-NS) on sleep and brain temperature (T-br). Rats were injected intraperitoneally with saline on the control day and with CC K-8-NS (10, 50, or 250 mu g/kg) or CCK-4 (10, 50, or 250 mu g/kg) on t he test day 5-10 min before dark onset. Electroencephalogram, electrom yogram, and T-br were recorded for 12 h. None of the treatments affect ed sleep or T-br significantly, with the exception of 10 mu g/kg CCK-4 , which transiently decreased the amount of NREMS, and 10 mu g/kg CCK- 8-NS, which slightly increased REMS. These results suggest that the ac tivation of CCK-B receptors by systemic injection of CCK-4 or CCK-8-NS is not sufficient to elicit increased NREMS and hypothermia in rats. (C) 1997 Elsevier Science Inc.