OXYTOCIN ACTIVATES THE POSTPARTUM ONSET OF RAT MATERNAL-BEHAVIOR IN THE VENTRAL TEGMENTAL AND MEDIAL PREOPTIC AREAS

Oxytocin binding (B-max) was found to be higher in the ventral tegmental area (VTA) and the medial preoptic area (MPOA) at midparturition compared with Pregnancy Days 15-17 or Postpartum Days 5-7 in rat dams. Pup retrieval and assuming a nursing posture over pups were blocked in parturient darns by infusions of an oxytocin antagonist into the VTA or MPOA and by infusions of a vasopressin (V-1) antagonist into the MPOA. These results implicate oxytocin in the VTA and MPOA and vasopressin in the MPOA, as well as a parturition-associated rise in oxytocin binding in these sites in the postpartum activation of maternal behavior.