Stress is accompanied by HPA activity, which results in the release of glucocorticoids into the blood. In general, glucocorticoids appear to inhibit adult neurogenesis in the dentate gyrus. Exogenous administration of corticosterone to rodents produces a decrease in the number of proliferating cells and surviving new granule neurons (Cameron & Gould, 1994; Wong & Herbert, 2006; Brummelte & Galea, 2010a). The suppressive action of corticosterone on cell proliferation seems to occur independent of sex (Brummelte & Galea, 2010a) and reproductive status (Brummelte & Galea, 2010b). By contrast to the negative actions of glucocorticoids on adult neurogenesis, removal of the adrenal glands by adrenalectomy (ADX), stimulates cell proliferation and adult neurogenesis in the dentate gyrus (Gould et al., 1992; Cameron & Gould, 1994). Taken together, these findings suggest that the rate of cell proliferation and adult neurogenesis in the dentate gyrus of adult rodents can be regulated by the levels of circulating glucocorticoids. Since glucocorticoid injections produce similar effects on adult neurogenesis as stress, it is likely that the stress-induced increases in glucocorticoid levels are responsible for the stress-induced decreases in
