THE NEUROSTEROID DEHYDROEPIANDROSTERONE-SULFATE (DHEAS) ENHANCES HIPPOCAMPAL PRIMED BURST, BUT NOT LONG-TERM, POTENTIATION

Dehydroepiandrosterone sulfate (DHEAS), which is synthesized in the br ain and in the periphery, is known to affect the excitability of hippo campal neurons. However, its influence on electrophysiological plastic ity has not been addressed. We have studied the effects of DHEAS on pr imed burst (PB) and long-term (LTP) potentiation, two electrophysiolog ical models of memory. PB potentiation is a lasting increase in the am plitude of the CA1 population spike produced by minimal (threshold) el ectrical stimulation; LTP is produced by more extensive (supra-thresho ld) stimulation. Whereas intermediate doses (24 and 48 mg/kg, s.c.) of DHEAS given to rats enhanced PB potentiation, low (6 mg/kg) and high (96 mg/kg) doses were ineffective. LTP was not affected by any dose of DHEAS. The inverted-U relationship between DHEAS and PB potentiation is consistent with previous work demonstrating an inverted-U dose-depe ndent enhancement of memory by DHEAS. The present findings suggest tha t DHEAS could enhance memory by facilitating the induction of neural p lasticity.