Type I adrenal steroid receptors prolong hippocampal long-term potentiation

The effects of Type I adrenal steroid receptors in prolonging synaptic plasticity in the dentate gyrus of freely behaving rats was investigated. Rats were implanted with chronic, bilateral stimulating and recording electrodes in the perforant pathway and dentate gyrus, respectively, and adrenalectomized (ADX). After a 2-3 day recovery period, baseline recordings of field potentials were made followed by administration of aldosterone or vehicle. One hour later, high frequency stimulation (HFS; chosen to produce comparable long-term potentiation (LTP) in the aldosterone-treated and control groups) was applied unilaterally and recording was continued for 1 h and again performed at 3, 24 and 48 h. LTP in ADX controls decayed significantly within 3 h, and returned to baseline levels at 24 h. In contrast, the aldosterone-treated animals showed enhanced LTP at 3, 24 and 48 h. These findings demonstrate that aldosterone both enhances and prolongs hippocampal plasticity.