Maternal modulation of infant glucocorticoid stress responses: Role of age and maternal deprivation

Abstract

We recently showed that maternal contact (passive contact with an anesthetized lactating dam) eliminates the corticosteroid response to novelty stress in 12-, 16-, and 20-day-old rat pups that have been deprived of food and maternal care for 24 h. Here we report two experiments in which we examined the role of deprivation in the stress-modulatory effect of maternal contact. Blood levels of plasma corticosterone were determined in three groups of infant rats: a basal not-tested (NT) group, a group placed alone in warm novel test arenas (pup alone, or PA), and a group exposed to novelty in the presence of an anesthetized lactating dam (DAM). These three treatment conditions were combined factorially with a deprivation variable; that is, prior to testing, half the pups were deprived of food and maternal care for 24 h, and half the pups remained with their mothers in the home nest. Experiment 1 employed this 2 (deprived vs. nondeprived) x 3 (NT vs. DAM vs. PA) factorial design at each of three ages: 12, 16, and 20 days postnatal. In Experiment 2 this design was employed at 20, 24, and 28 postnatal days of age. At 12, 16, 20, and 24 days of age, deprived pups displayed a robust glucocorticoid response to novelty stress, and this response was inhibited by maternal contact. Nondeprived animals, on the other hand, displayed a dramatically attenuated glucocorticoid response to novelty that was less effectively inhibited by maternal contact. At 28 days, maternal contact was relatively ineffective in inhibiting the stress response, particularly in the absence of deprivation. These findings replicate and extend our previous ones concerning the psychological control of the pituitary-adrenal system during development and are consistent with the notion of maternal regulation of this physiological system in the infant. © 1988, Psychonomic Society, Inc.. All rights reserved.