Plasma corticosterone fluctuations in an infant-learning paradigm.
Plasma corticosterone fluctuations of infant rats were examined in a learning task. A blood sample for analysis of plasma corticosterone was collected from groups of 10- and 15-day-old pups following either no disturbance, standard maternal deprivation only, or deprivation and training in an established approach-mother, avoid-shock conflict task. In the latter condition, pups remained in the goalbox either alone or with an anesthetized dam for either 15 or 60 min before blood sample collection. Plasma corticosterone levels were elevated following deprivation plus training in pups of both ages and following deprivation only in the 15-day-old pups. Further, the presence of the dam in the goalbox reduced plasma corticosterone elevations, particularly among 15-day-old pups and at 60 min. These findings suggest that the mother's capacity to moderate the pup's plasma corticosterone response may contribute to her reinforcement value in infant-learning paradigms.