Dehydroepiandrosterone (DHEA), an adrenal cortex hormone secreted in large quantities in humans, protects cells of the clonal mouse hippocampal cell line HT-22 against the excitatory amino acid glutamate (5 mM), and amyloid beta-protein (2 microM) toxicity in a dose-dependent manner with optimum protection obtained at 5 microM concentration of DHEA. The protective effects of DHEA appear to be specific in that other related steroids and metabolites of DHEA, such as 5-androstene-3beta,17beta-diol, etiocholan-3alpha-ol-17-one, etiocholan-3beta-ol-17-one, testosterone, and 5alpha-androstane-3, 17-dione, offered no protection even at 50 microM concentrations. In addition, using immunocytochemical techniques, we observed that 20 hr of treatment with 5 mM glutamate remarkably increased glucocorticoid receptor (GR) nuclear localization in neuronal cells. Interestingly, 5 microM DHEA treatment for 24 hr, followed by 5 mM glutamate treatment for 20 hr almost completely reversed the copious nuclear localization of GR observed by glutamate treatment alone. Results obtained suggest that DHEA protects hippocampal neurons, at least in part, by its antiglucocorticoid action via decreasing hippocampal cells nuclear GR levels.