Figure 4.
Post-training systemic E2 injection enhances spatial memory consolidation in the Morris water maze and object recognition memory consolidation in ovariectomized mice. (A) Ovariectomized mice received eight hidden-platform training trials prior to E2 administration. Immediately after the final training trial (arrow), mice were injected with cyclodextrin vehicle (Control) or one of three doses (0.1, 0.2, or 0.4 mg/kg) of cyclodextrin-encapsulated E2. When memory for the platform location was tested 24 h later, only mice injected with 0.2 mg/kg E2 remembered the platform location as indicated by the fact that mice in all other groups swam significantly longer distances on day 2 compared with mice in the 0.2 mg/kg group (*P < 0.05). (B) Ovariectomized mice accumulated 30 sec exploring two identical objects and then were immediately injected with cyclodextrin vehicle (Control) or one of three doses (0.1, 0.2, or 0.4 mg/kg) of cyclodextrin-encapsulated E2. During testing 48 h later, mice receiving 0.2 or 0.4 mg/kg E2 spent significantly more time with the novel object than chance (dashed line at 15 sec), indicating that these doses enhanced object recognition memory consolidation (*P < 0.05 relative to chance). In contrast, the control and 0.1 mg/kg groups did not spend more time than chance with the novel object. Error bars in both panels represent the mean ± SEM. (Adapted from Gresack and Frick 2006 with permission from Elsevier © 2015.)