PERIODIC MATERNAL-DEPRIVATION ALTERS STRESS-RESPONSE IN ADULT OFFSPRING - POTENTIATES THE NEGATIVE FEEDBACK-REGULATION OF RESTRAINT STRESS-INDUCED ADRENOCORTICAL-RESPONSE AND REDUCES THE FREQUENCIES OF OPEN FIELD-INDUCED BEHAVIORS

The effects of periodic maternal deprivation (PMD) treatment on the ad renocortical stress response and on open-field behavior in adult offsp ring were investigated. Sprague-Dawley rat pups were deprived of mothe rs daily for 4.5 h during the first 3 weeks of life. PMD treatment res ulted in lower corticosterone levels during restraint stress later in life. The result of dexamethasone suppression test indicated that PMD treatment caused a potentiation of the negative feedback function of a drenocortical response. These effects of PMD were not accompanied by a n increased density of the hippocampal glucocorticoid receptor which h as been reported to be induced in neonatal handling treatment (brief 1 5-min maternal deprivation). Serotonin (5-HT)-2 and beta-adrenergic bi nding sites were also examined in cerebral cortex and no change of bin ding capacities were induced by PMD treatment. In the open-field test, PMD treatment decreased the number of ambulations and rearings but di d not affect a frequency of defecation. From these results, it is sugg ested that PMD treatment leads rats to be insensitive to environmental stimuli in adulthood.