Effects of intraventricular implantation of crystalline estradiol benzoate on the sleep-wakefulness circadian rhythm of ovariectomized rats.

The effect of estrogen on the sleep-wakefulness circadian rhythm was examined in ovariectomized rats. Implantation of crystalline estradiol benzoate (EB) into the third cerebral ventricle reduced the slow wave sleep (SWS) and paradoxical sleep (PS) appearances within the dark period. This result was similar to that obtained by a systemic administration of 20 micrograms of EB. The inhibition of sleep during the nighttime was more remarkable in PS than in SWS. The reduction of SWS was due to a shorter duration of SWS episodes and the reduction of PS to a fewer number of PS episodes. These results indicate that ovariectomized rats treated with estrogen develop an inability to sustain episodes of SWS and initiate PS episodes.