The role of the estrogen receptor alpha in the medial amygdala and ventromedial nucleus of the hypothalamus in social recognition, anxiety and aggression.

Social recognition manifests itself in decreased investigation of a previously encountered individual. Estrogen receptor alpha (ERalpha) knock out mice show deficient social recognition and anxiety. These data show that the ERalpha is involved in these effects, but they do not say anything about the brain sites important for these effects. In this study, an shRNA encoded within an AAV viral vector directed against the ERalpha receptor gene (or containing luciferase control), was injected bilaterally into the posterodorsal amygdala (MePDA) or the ventromedial nucleus of the hypothalamus (VMN) of female rats. An 81% reduction of ERalpha expression in the MePDA eliminated social recognition. Moreover, this diminution of ERalpha in the MePDA reduced anxiety in the light/dark choice test. In contrast, social recognition was unaffected after ERalpha knockdown in the VMN while aggressiveness against the juvenile was enhanced. In conclusion, social recognition and anxiety in female rats are modulated by the ERalpha in the amygdala. Moreover, aggression against juveniles but not against adults could, at least partly, depend on the ERalpha in the VMN.