Mother-infant interaction and the modulation of pituitary-adrenal activity in rat pups after early stimulation.

In Experiment I, handling or electric shock of 2-day-old rat pups triggered pituitary-adrenocortical activity. Interaction between mother and litter after pup treatment affected the magnitude and the time course of the pups' adrenocortical response. Mother-infant interactions following pup treatment on Day 2 were found to affect the responsiveness of pups to later stimulation. In Experiment II handled or shocked pups that were returned to a mother-absent nest were subsequently found to be less responsive to ACTH injection than were pups returned to a mother-present next following treatment. These data are discussed in terms of the reciprocity and synchrony in mother-infant interactions and the Maternal Mediation hypothesis of early experience.