Increase of paradoxical sleep by electrical stimulation within lateral ventricles of rat

The effect on the sleep-waking cycle of low intensity electrical stimulation (0.2 mA intensity, 80 Hz frequency, 0.7 ms signal duration) within the lateral ventricles was studied in rats maintained under a photoperiod of 12 h light and 12 h darkness (lights on at 06.00 h). When stimulation was performed at 1700 h for 3 min, there was a significant immediate increase in paradoxical sleep (PS) and slow wave sleep (SWS) during the hours of darkness, followed by a delayed increase in diurnal PS amounts during subsequent days. These results are discussed with reference to mechanisms involving the pineal gland and serotonergic system on both the immediate and long-lasting PS effects.