Pregnenolone sulfate increases hippocampal acetylcholine release and spatial recognition

The pregnenolone sulfate is a neurosteroid with promnesic properties. Recently, a correlation between endogenous levels of pregnenolone sulfate in the hippocampus and performance in a spatial memory task has been reported in aged rats. Cholinergic transmission is known to modulate memory processes and to be altered with age. In the present experiment we investigated the effect of increasing doses of pregnenolone sulfate on hippocampal acetylcholine release. Our results show that intracerebroventricular administrations of this neurosteroid induced a dose-dependent increase in acetylcholine release. Administration of 12 and 48 nmol of pregnenolone sulfate induced a short lasting (20 min) enhancement of acetylcholine output with a maximum around 120% over baseline and the administration of 96 and 192 nmol doses induced a long-lasting (80 min) increase that peaked around 300% over baseline. In a second experiment we have observed that the 12 nmol dose enhanced spatial memory performance, whereas the 192 nmol dose was inefficient. These results are consistent with previous work suggesting that, a modest increase in acetylcholine release facilitates memory processes, while elevation beyond an optimal level is ineffective. Nevertheless, neurosteroids may be of value for reinforcing depressed cholinergic transmission in certain age-related memory disorders. (C) 2000 Elsevier Science B.V. All rights reserved.