FIGURE 3.

Age and estradiol interact to differentially regulate the number of ER-labeled synapses and ER α and ER β within the synapses in the hippocampus of ovariectomized female rats receiving estradiol for 2 days. Top left: the percentage of ER α-labeled synapses decreases with age (*P < 0.0001); however, there is no effect of estradiol (E2) treatment in either group on the number of synapses containing ER α (both P values > 0.31). Top right: the percentage of ER β-labeled synapses decreases with age (⁺P < 0.02). Estradiol treatment increases the percentage of ER β-labeled synapses in both age groups (*P < 0.0001). Bottom left: in young and aged females, estradiol affects the distribution of ER α labeling in the pre- and postsynaptic compartments most distal from the synaptic cleft. Bottom right: estradiol but not age affects ER β distribution within the synapse. In both groups, estradiol increases ER β within the postsynaptic density. Histograms and diagrams are plotted and drawn, respectively, from data originally presented in Adams et al. (2) and Waters et al. (227).