The role of the estrogen receptor α 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 (ERα) knock out mice show deficient social recognition and anxiety. These data show that the ERα 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 ERα 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 ERα expression in the MePDA eliminated social recognition. Moreover, this diminution of ERα in the MePDA reduced anxiety in the light/dark choice test. In contrast, social recognition was unaffected after ERα knockdown in the VMN while aggressiveness against the juvenile was enhanced. In conclusion, social recognition and anxiety in female rats are modulated by the ERα in the amygdala. Moreover, aggression against juveniles but not against adults could, at least partly, depend on the ERα in the VMN.