Figure 6.

Effects of post-training estradiol on memory consolidation in young ovariectomized mice. (A) 0.2 mg/kg E₂ significantly improved spatial memory retention in the Morris water maze. All groups learned to find the platform similarly on Day 1 (training trials 1–8). Mice were injected intraperitoneally (i.p.) with vehicle or E₂ immediately following trial 8 (arrow). Twenty-four hours later, only mice receiving 0.2 mg/kg E₂ remembered the platform location, as indicated by shorter swim distances on Day 2 relative to vehicle controls and mice receiving 0.4 mg/kg E₂ (*p < 0.05). Each point represents the mean (± SEM) for a single trial. (B) During object recognition testing, groups receiving 0.2 mg/kg or 0.4 mg/kg E₂ spent significantly more time than chance (dashed line at 15 seconds; *p < 0.05) with the novel object 48 hours after injection), suggesting intact memory for the familiar object. (A) and (B) reprinted from (Gresack and Frick, 2006b). (C) Intrahippocampal infusion of E₂ immediately, but not 3 hours later, also enhances novel object memory consolidation. Mice receiving immediate bilateral dorsal hippocampal infusions of 5 μg E₂, but not vehicle, spent significantly more time than chance with the novel object 48 hours after infusion (dashed line at 15 seconds; *p < 0.05). For both panels, each bar represents the group mean (± SEM) for the retention trial. Adapted from (Fernandez et al., 2008).