Development of behavioral and neuronal responses to social stress: early adolescence as a sensitive period

Abstract

The research goal was to determine whether social stress differentially impacts on behavior and brain physiology during critical windows in adolescent development. Early adolescent (EA), mid‐adolescent (MA) and adult rats were exposed to 7 days of a social stressor, the resident‐intruder paradigm. Social stress had divergent effects on behavior in EA and adult rats, promoting active coping behaviors in EA rats and decreasing active coping behaviors in adult rats as determined by the defensive burying test and response to swim stress. Mid‐adolescent rats exposed to social stress showed no changes in the behavioral endpoints. Effects of social stress in EA rats was not mimicked by chronic restraint stress. Because the locus coeruleus (LC)‐norepinephrine system has been implicated in certain active coping behaviors, LC neuronal activity was recorded in EA rats exposed to social stress and matched controls. LC spontaneous firing rates were higher in EA rats exposed to social stress. Moreover, intra‐LC infusion of the CRF antagonist, DPheCRF12‐41, inhibited LC neurons of stressed rats but not controls. These data suggest that exposure to social stress in early adolescence promotes tonic secretion of CRF into the LC to activate this system. This CRF‐induced activation of the LC‐norepinephrine system may underlie the promotion of active‐coping behaviors noted in socially stressed EA rats.MH058250