Developmental effects of oxytocin on stress response: single versus repeated exposure.

Both exogenous and endogenous oxytocin (OT) are associated with an attenuated stress response. Increased levels of OT in the early postnatal period have been shown to affect behavior and physiology in rodents, and these effects last into adulthood, suggesting an organizational role for OT during development. We investigated the effects of neonatal exposure to OT on the development of the stress response in male and female prairie voles (Microtus ochrogaster). OT or an OT antagonist (OTA) was administered either on postnatal day 1 (single, D1) or days 1-7 (repeated, D1-7) and then on day 8 the response to social isolation was assessed by quantifying ultrasonic vocalizations (USVs) and measuring plasma corticosterone (CORT). Treatment effects were observed only in females. A single treatment with OTA was associated with a decrease in vocalizations, while repeated treatment produced an increase in vocalizations. A single treatment with either saline or OTA increased basal CORT. The results suggest that endogenous OT may be involved in the development of the stress response in females.