EEG power spectra in rats during compression and during pentobarbital infusion at pressure

The EEG of rats was studied with power spectrum analysis under compression to 71 ATA with He-O2 and during constant rate infusion of pentobarbital at 71 ATA and at surface. During compression the 1-4 Hz delta activity was increased, and 8-11 Hz alpha, 12-14 Hz spindle, and 16-10 Hz low beta activities were reduced compared to control animal recordings. During the course of pentobarbital infusion at 71 ATA, this picture changed: the delta activity was reduced while alpha and spindle activities (barbiturate spindles) increased, considerably more than in the rats studied at surface pressure. The findings may only in part be explained by pressure reversal of anesthesia.