A CCKA-RECEPTOR ANTAGONIST ADMINISTERED TO THE NEONATE ALTERS MOTHER-INFANT INTERACTIONS IN THE RAT

The importance of the infant's cholecystokinin (CCK) system for elicit ing optimal maternal care was examined in 6-9-day-old Sprague-Dawley r ats. After administration of either vehicle, CCK-8 (1 or 8 mu g/kg) or devazepide (1 mg/kg; a selective CCKA receptor antagonist), pups were either individually isolated (Experiment 1) or individually reunited with their dam (Experiment 2) and the rats' behavior was observed. Whe n isolated, pups that received devazepide displayed significantly more head-lifting and wall-climbing attempts than vehicle-treated controls , suggesting that endogenous CCK dampens activity. Devazepide-treated rats were found more frequently in proximity with their mothers when r eunited with them, and they emitted more ultrasonic vocalizations comp ared to vehicle controls. Pups treated with 1 mu g/kg CCK received les s body licking than vehicle controls. In addition, dams hovered and cr ouched over devazepide-treated pups more than over pups treated with 1 mu g/kg CCK. The results suggest that endogenous CCK has a calming, q uieting effect in the neonatal pup and that this, in turn, results in less infant-mother attractivity and reduced levels of maternal care. ( C) 1998 Elsevier Science Inc.