ABSTRACT
Dysfunction in central glucocorticoid signaling is implicated in hypothalamic-pituitary-adrenocortical (HPA) axis dysregulation and major depression. In comparison with men, women are twice as likely to suffer from depression and have heightened HPA axis responses to stress. We hypothesized that this striking increase in stress vulnerability in females may be because of sex differences in central glucocorticoid signaling. The current study tests the role of the forebrain type II glucocorticoid receptor (GR) on HPA axis function in female mice and depression-like behavior in both female and male mice. This was accomplished by using mice with selective deletion of GR in forebrain cortico-limbic sites including the prefrontal cortex, hippocampus, and basolateral amygdala (forebrain glucocorticoid receptor knockout mouse (FBGRKO)). In order to examine HPA axis function in female FBGRKO, we measured nadir, peak circadian and restraint-induced corticosterone concentrations in female FBGRKO. The data indicate that unlike male FBGRKO, basal and stress-induced corticosterone concentrations are not increased in female FBGRKO. Given the pronounced effect of central glucocorticoid signaling on mood, we also examined the necessity of corticolimbic GR on depression-like behavior with the sucrose preference and forced swim tests (FST) in male and female FBGRKO mice. Consistent with previous studies, male FBGRKO displayed increased depression-like behavior as indicated by greater immobility in the FST and decreased sucrose preference compared with littermate controls, effects that were not observed in females. Overall the findings indicate a marked sex difference in the function of forebrain GR on HPA axis regulation and depression-like behaviors, and may have implications for therapeutic approaches using GR-modulating drugs.
