Estrogen receptor alpha influences socially motivated behaviors.

Male mice lacking estrogen receptor alpha (ERalphaKO) show reduced social behaviors. We hypothesized that this might be due to either socially elicited or generalized anxiety. Male ERalphaKOs and wild type (WT) mice were given a series of behavioral tests: elevated plus maze, T-maze, and social recognition. Each test included a social dimension by exposing males to ovariectomized (OVX) females. In addition plasma concentrations of corticosterone were measured, and open field activity was assessed. In the elevated plus maze, WT males exposed to an OVX female 1 min prior to the test were more anxious than WT controls. ERalphaKO males showed anxiety in this test whether or not they were preexposed to a female. In the T-maze, WT males increased exploration of a novel arm when it contained an OVX female. The presence or absence of a female in a novel arm did not affect behavior of ERalphaKO males. In social recognition tests, ERalphaKO males spent less time than WT littermates investigating an OVX female that was repeatedly introduced into their home cage. On the final trial, when a novel female was introduced, WT males increased their chemo-investigation but ERalphaKOs did not. Plasma corticosterone levels were lower in ERalphaKO than in WT males when plasma was taken directly after a brief (control) cage disturbance. In the open field WT and ERalphaKO males behaved essentially the same. Taken together, the results of these experiments suggest the ERalphaKO males avoid contact with other conspecifics, perhaps due to an inability to be aroused by social cues.