Figure 7.

Estradiol selectively activates a RhoA-to-actin signaling pathway. Hippocampal slices (male rats) were treated with vehicle (Veh) or 1 nm estradiol (E2) for 20 min. A, Representative Western blots show at left levels of phosphorylated (p) cofilin and total cofilin and at right levels of pPAK and total PAK1 in hippocampal slices treated with vehicle or E2. Quantitative analyses (n = 6 slices/group) confirmed that E2 selectively increased levels of pCofilin relative to total cofilin (bar graph; p < 0.05 for E2 vs Veh), whereas E2 modestly but significantly reduced pPAK relative to measures from vehicle controls (n = 8/group; p < 0.01). Total PAK levels were unaffected. B, Total and active (GTP-bound) levels of RhoA, Cdc42, and Rac in vehicle- and E2-treated slices as seen in Western blots of material collected with the pull-down assay. Plots of band densities (bottom panel) indicate that E2 increased slice concentrations of activated RhoA (n = 3–5/group; p < 0.05 vs Veh control) while having no effect on total RhoA. Results from similar experiments detected no effect of E2 on active or total levels of the related GTPases Rac and Cdc42. Following a 60 min washout of E2, activated RhoA levels were not significantly different from those in vehicle-treated slices (n = 3/group). C, The ROCK inhibitor H-1152P (250 nm; open horizontal bar) reversibly blocked the increase in synaptic responses induced by E2 (n = 4). Inset, Representative traces collected during treatment with H-1152P, and E2 alone and in combination. Calibration: 1 mV, 5 ms.