Sleep cycles in cats during chronic electrical stimulation of the area postrema and the anterior raphe

Sleep-waking profiles were obtained from 130 7 hr stimulation-EEG recording sessions in a series of cats bearing chronically implanted stimulating electrodes in the regions of the area postrema and anterior raphe nuclei. The results indicated that: (a) during electrical stimulation of the region of the area postrema with 0.5 or 10 Hz at 1 and 2 mA there were significant increases in the occurrence of the deeper aspects of slow-wave sleep and in REM sleep. These elevations were significant in comparison to nonstimulation baselines and to sleep profiles obtained during stimulation of points located dorsal and anterior to the area postrema. (b) Stimulation of the medial reticular formation including the anterior raphe using the same parameters employed for the area postrema did not alter the occurrence of any stage of sleep. These findings indicate that the region of the area postrema may be more involved in the generation of sleep than the anterior raphe nuclei.