SLEEP-WAKING CYCLE IN CHRONIC RAT PREPARATIONS WITH BRAIN-STEM TRANSECTED AT THE CAUDOPONTINE LEVEL

The brain stem of rats was transected at the middle of the nucleus ret icularis pontis caudalis. The preparations were maintained 2-9 days, a nd their EEG activity and behavior were studied. Maintained EEG activi ty and EEG arousal to visual and olfactory stimuli indicated the prese nce of sleep-waking cycle. Three stages were identified. Two of them c orresponded to waking with hippocampal theta rhythm and to slow wave s leep in intact rats. The third stage (absent in intact rats) was chara cterized by slow waves and spindles of low amplitude in the cortex and low frequency theta rhythm, and it was considered as ''drowsiness.'' Waking without theta rhythm, paradoxical sleep, and its forerunner int ermediate stage were never found. Paroxystic-like EEG episodes were fr equently observed. Thus, although present, the sleep-waking cycle is s everely impaired in the caudopontine rats. The impairment is similar t o that found previously in rats transected at the intercollicular or p retrigeminal level. The preparations were able to crawl abortively and to swallow liquid. Their respiratory rhythm was normal, but the heart rate increased. Thus, the caudal part of the preparations showed rema rkable ability in controlling motor and vegetative functions.