Sexual differentiation of oxytocin stress responsiveness: effect of neonatal androgenization, castration and a luteinizing hormone-releasing hormone antagonist.

The plasma OT increment following stress in rats is sexually dimorphic, females exhibiting greater responses than males. We have investigated the role of neonatal androgen secretion in determining the sex-typical level of response. Castration of male pups either surgically or functionally (GnRH antagonist treatment) within either 2 h or 5 days of birth did not elevate the OT responses of adult males. In contrast, androgenization of female pups (testosterone, 1.25 mg/pup) within 5 days of birth markedly reduced the OT stress responses of adults to a level insignificantly different to males. The results show that neonatal androgens can exert organizational effects on OT regulatory mechanisms. Since neonatal castration was ineffective it would appear that a prenatal defeminization or masculinization event determines OT stress responsiveness in males.