Figure 3.

Effects of estrogen receptor stimulation on the threshold and ceiling for LTP in field CA1. A, Two or three theta bursts (arrows) did not reliably change the fEPSP slope in hippocampal slices (male rats) continuously infused with vehicle (0.01% DMSO) or the ER-α agonist PPT, but produced stable potentiation following pretreatment with estradiol (E2) or the ER-β agonist WAY. Five or ten theta bursts (arrows) generated greater potentiation in E2- or WAY-treated slices than in vehicle- or PPT-infused slices (n = 5/group). The upper dashed line denotes maximum LTP during control (aCSF) conditions. Inset: Traces collected during baseline recording (solid line) and 30 min after delivery of 3, 5 or 10 theta bursts (dotted lines) from slices infused with vehicle, E2 or WAY. Calibration: 1 mV, 5 ms. B, Percentage increase in burst response area across a series of 10 theta bursts in vehicle, PPT, WAY, and E2-treated slices; within-train facilitation was not significantly different between groups. C, Traces show the composite responses generated by a pair of theta bursts (200 ms between-burst interval) recorded in the presence and absence of 100 μm APV; percentage change in the areas of the fourth EPSP (red hash marks) provides a measure of NMDA receptor-mediated depolarization (calibration: 1 mV, 10 ms). As described in text, E2 did not affect this component of burst responses used to induce LTP (n = 4).