The neurosteroid dehydroepiandrosterone sulfate (DHEAS) enhances hippocampal primed burst, but not long-term, potentiation

Dehydroepiandrosterone sulfate (DHEAS), which is synthesized in the brain and in the periphery, is known to affect the excitability of hippocampal neurons. However, its influence on electrophysiological plasticity has not been addressed. We have studied the effects of DHEAS on primed burst (PB) and long-term (LTP) potentiation, two electrophysiological models of memory. PB potentiation is a lasting increase in the amplitude of the CA1 population spike produced by minimal (threshold) electrical stimulation; LTP is produced by more extensive (supra-threshold) 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-dependent enhancement of memory by DHEAS. The present findings suggest that DHEAS could enhance memory by facilitating the induction of neural plasticity.