Estrogen receptors and the social brain

The relationship between the patterns of estrogen receptor (ER) alpha expression in discrete brain regions and reproductive behavior was examined. It was hypothesized that increased ERalpha expression would be associated with enhanced sexual behavior and reduced prosocial behavior, whereas decreased ERalpha expression would be associated with reduced sexual behavior and enhanced prosocial behavior.;All of the experiments in this work focused on ERalpha expression in the medial preoptic area (MPOA), ventromedial nucleus of the hypothalamus (VMH), posterodorsal medial amygdala (MePD) and bed nucleus of the stria terminalis (BST), as these interconnected regions express high levels of ERalpha and are known to directly regulate reproductive behavior.;Neonatal manipulations that modified the signaling or expression of ERalpha were found to alter the organization of reproductive behavior. For example, neonatal oxytocin antagonist treatment reduced hypothalamic ERalpha expression and reduced sexual receptivity in adult female rats. Additionally, neonatal ERalpha activation reduced subsequent prosocial behavior in juvenile male prairie voles.;Manipulations of the social environment in adulthood also altered ERalpha expression and reproductive behavior, suggesting that the plasticity of the ER system persists beyond early development and may serve to coordinate future reproductive behavior with changes in the current social environment in order to optimize reproductive success.;Collectively, these data support the hypothesis that central ERalpha expression is a critical regulator of reproductive behavior in both males and females and indicate that ERalpha expression in specific brain regions may differentially contribute to species-, sex- and individual differences in behavior. Specifically, hypothalamic ERalpha expression appears to directly gate the production of various reproductive behaviors, whereas extra-hypothalamic ERalpha expression appears to contribute to the temporal modulation and fine-tuning of behavior, possibly via changes in sensory feedback mechanisms. Thus, these data contribute to the understanding of how ERalpha expression in discrete brain regions contributes to the overall pattern of reproductive behavior in males and females.