The effect of perinatal exposure to estrogens on the sexually dimorphic response to novelty.

In this study we investigated the sexually dimorphic anxiety response to a novel environment in the absence of estrogens neonatally or in adulthood. There was a sexual dimorphism in the plus-maze test after the open-field test, females being more active and less anxious. In the absence of estrogens neonatally but not in the adulthood, the activity levels were similar to those shown by females, while the anxiety level was similar to males. These results suggest the need of a normal estrogen environment during the critical period of development for the normal differentiation of female anxiety responses to a novel environment.