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

Population excitatory post-synaptic potentials (pEPSPs) were recorded in vitro from subfield CA1 of the hippocampus of female rats which had been ovariectomized and treated for 14 days with either oil or 17beta-oestradiol (10 microg/day). The currents applied to the Schaffer collateral-commissural input necessary to induce threshold, maximum and 50% maximum pEPSP responses did not differ between groups. Application of trains of pulses (0.1-1 s; 100 Hz) evoked post-tetanic and long-term (> 60 min) potentiation of pEPSP responses, the magnitude of which was related to stimulus duration in both groups. 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 and glutamatergic and GABAergic components of the inputs to CA1, these data suggest that chronic oestradiol treatment has no effect on either the excitability or induction of LTP in the Schaffer collateral-commissural-CA1 pathway.