Figure 3.

(A) Schematic of the novel object recognition testing protocol. Mice accumulate 30 seconds exploring two identical objects in an open arena. Immediately post-training, mice are infused and then returned to their home cage. Retention is tested 24 or 48 hours later by presenting mice with one novel and one familiar object. Mice who remember the familiar object spend more time than chance (15 sec) exploring the novel object. (B) The HDAC inhibitor TSA enhances novel object recognition memory consolidation. Ovariectomized female mice given bilateral infusions of vehicle into the dorsal hippocampus immediately after training spent significantly more time than chance (dashed line at 15 sec; *p < 0.05 relative to chance) with the novel object 24 hours after infusion, but not 48 hours after infusion, suggesting that they did not remember the familiar object for 48 hours. In contrast, mice given bilateral infusions of TSA (16.5 mM/hemisphere) into the dorsal hippocampus immediately after training did spend significantly more time than chance (*p < 0.05) with the novel object 48 hours later. However, this memory enhancement was not observed if TSA infusion was delayed for three hours. These data suggest that histone acetylation enhances novel object memory consolidation. Bars represent the mean ± SEM for each object. Panel B reprinted with permission from (33).