Sex-specific effects of neonatal progestin receptor antagonism on juvenile social play behavior in rats.

Developing mammals are exposed to progesterone through several sources; however, the role of progesterone in early development is not well understood. Males express more progestin receptors (PRs) than females within several brain regions during early postnatal life, suggesting that PRs may be important for the organization of the sex differences in the brain and behavior. Indeed, previous studies showed cognitive impairments in male rats treated neonatally with a PR antagonist. In the present study, we examined the role of PRs in organizing juvenile behaviors. Social play behavior and social discrimination were examined in juvenile male and female rats that had been treated with CDB, a PR antagonist, during the first week of postnatal life. Interestingly, neonatal PR antagonism altered different juvenile behaviors in males and females. A transient disruption in PR signaling during development had no effect on social discrimination but increased play initiation and pins in females. These data suggest that PRs play an important role in the organization of sex differences in some social behaviors.