Psychological stress and administered oxytocin during pregnancy: effect corticosterone and prolactin response in lactating rats.

Recent evidence suggests that oxytocin modulates both ACTH and prolactin secretion. The present study was designed to investigate the possible role of oxytocin in the corticosterone and prolactin response to predictable and unpredictable novelty stress. These responses were examined in lactating females (Day 6 and Day 21 postpartum) which had received stress and oxytocin treatment during pregnancy. The results demonstrated that exposure to the novelty stressors during pregnancy resulted in a significant elevation in corticosterone levels of lactating females on Day 6 postpartum. A similar elevation was also observed on Day 21 postpartum for the unpredictable condition. Oxytocin treatment did not, however, significantly affect the corticosterone response to the psychological stressor. Furthermore, prolactin levels were not significantly affected on either Day 6 or Day 21 postpartum by either novelty stress or oxytocin treatment administered during pregnancy. It was suggested that the sustained elevation in corticosterone levels obtained following unpredictable exposure to the stressor had important implications for the lactation process.