Oxytocin antagonism alters rat dams' oral grooming and upright posturing over pups.

Studies involving intracerebral administration of antiserum or antagonists have demonstrated that central oxytocin (OT) plays a prominent role in initiating but not maintaining postpartum maternal behavior in rats. There has been little investigation, however, of OT's influence on the levels of maternal behavior exhibited during the maintenance phase. We measured rat dam behavior during the 105-min observation periods preceding and beginning 2 h after intracerebroventricular infusion of the selective OT antagonist (OTA) (1 microg), or normal saline (NS) vehicle (5 microl) on postpartum days 2-3 and 6-7. Compared to NS, OTA significantly decreased pup licking as a proportion of dams' total oral grooming, increased self-grooming, decreased the frequency of elevated upright posture over pups and increased the frequency of lying prone on pups. Quiescent, kyphotic nursing was also significantly lower in OTA-treated dams. Other components of maternal behavior were not significantly affected by OTA or NS treatment. These findings suggest that central OT may shift the focus of the dams' oral grooming from self to pups and may also facilitate elevation of dams' upright posture over pups. Acute stress responses, maternal behavior and central OT receptor binding in adult rats have been linked to the amount of maternal licking and arched back, upright nursing received during infancy. OT activity in dams' brains may influence these developmental outcomes in their offspring by selectively regulating their pup licking and crouching posture.