Chronic treatment with oestradiol does not after in vitro LTP in subfield CA1 of the female rat hippocampus

Population excitatory post-synaptic potentials (pEPSPs) were recorded in vi tro from subfield CA1 of the hippocampus of female rats which had been ovar iectomized and treated for 14 days with either oil or 17 beta-oestradiol (1 0 mu g/day). The currents applied to the Schaffer collateral-commissural in put necessary to induce threshold, maximum and 50% maximum pEPSP responses did not differ between groups. Application of trains of pulses (0.1-1 s; 10 0 Hz) evoked post-tetanic and long-term (> 60 min) potentiation of pEPSP re sponses, the magnitude of which was related to stimulus duration in both gr oups. However, the degree of potentiation induced by near-threshold (0.1, 0 .15 and 0.2 s) and saturating (1 s) stimuli did not differ between groups. Thus, despite reports that oestradiol can modulate synaptic spine density a nd glutamatergic and GABAergic components of the inputs to CA1, these data suggest that chronic oestradiol treatment has no effect on either the excit ability or induction of LTP in the Schaffer collateral-commissural-CA1 path way. (C) 1999 Elsevier Science Ltd. All rights reserved.