Intraperitoneal cholecystokinin-8 induces atypical somnolence and EEG changes.

EEG sleep recordings were performed in rats after administration of CCK-8. Mildly food-deprived rats were given IP CCK-8 (8 and 16 micrograms/kg body weight) and behavioural as well as EEG changes were examined. With 16 micrograms/kg of CCK-8, there was a significant increase of slow wave sleep in the 30 min of recording. Paradoxical sleep was unchanged or slightly decreased. The low dose of CCK-8 did not promote sleep. In addition both doses of CCK-8 induced EEG alterations including the presence of unusual acute spikes and slowing of EEG rhythm concomitant with awake immobility in rats. The computerized spectral analysis showed that CCK-8 slowed the EEG-wave frequency without modifying the total power energy in comparison with control wakefulness. In contrast, there was no effect in alcuronium-immobilized rats after 8 to 32 micrograms/kg IP of CCK-8. These observations do not support the idea that CCK-8, as a satiating factor like food, would promote sleep.