Estrogen receptor-alpha knockouts and maternal memory in nulliparous rats.

The current study investigated the role of estrogen receptor alpha (Esr1) in maternal memory in rats, comparing the induction and retention responses of Esr1 knockout (KO) and wild type (WT) nulliparous rats towards foster pups. Thirty days after completion of induction testing, subjects were tested for the retention of maternal care in their home cage and then for maternal behaviors in a novel cage. Both WT and Esr1 KO females displayed similar latencies to respond to foster young during the initial induction testing. Likewise, reinduction latencies to display full maternal responsiveness were similar in the Esr1 KO and WT groups during maternal memory testing in the home cage. However, in the novel cage testing WT subjects displayed modest modifications in maternal care. WT females had shorter latencies to first retrieve and mouth a test pup. These findings suggest that while Esr1 does not appear to affect the establishment of maternal care or the display of maternal memory, it may modulate aspects of pup-directed behaviors associated with the reinduction of maternal care in female rats.