Social recognition manifests itself in decreased investigation of a previously encountered individual.
Estrogen receptor alpha (ER) knock out mice show deficient social recognition and anxiety. These data
show that the ERis 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 ER
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 ER
expression in the MePDA eliminated social recognition. Moreover, this diminution of ER in the MePDA
reduced anxiety in the light/dark choice test. In contrast, social recognition was unaffected after ER
knockdown in the VMN while aggressiveness against the juvenile was enhanced. In conclusion, social
recognition and anxiety in female rats are modulated by the ER in the amygdala. Moreover, aggression
against juveniles but not against adults could, at least partly, depend on the ER in the VMN.