The promnesic neurosteroid pregnenolone sulfate increases paradoxical sleep in rats

The effect of systemic administration of the neurosteroid pregnenolone sulf ate (PREG-S) on sleep-wakefulness cycle and on spatial memory performances was investigated in male Sprague-Dawley rats, in the first experiment, the effect of PREG-S administration (saline, 4.75, 47.5 mg/kg, i.p.) on 24 h EE G recording was evaluated. In the second experiment, spatial memory perform ance in a two-trial memory task was evaluated after post-acquisition admini stration of similar doses of PREG-S as in the first experiment. Results sho w that PREG-S increases paradoxical sleep and improves the performance on t he memory task yielding similar dose response curves. Starting 4 h after ad ministration of 47.5 mg/kg PREG-S, paradoxical sleep is increased for 10 h. The PREG-S effect on spatial memory lasts for at least 24 h after injectio n. These results suggest that an enhancement of paradoxical sleep may be in volved in the promnesic effects of this neurosteroid. (C) 1999 Elsevier Sci ence B.V. All rights reserved.