Corticosterone (CORT) induces responses in brain cells that are mediated by glucocorticoid receptors through regulation of gene activity. We previously found rapid increases in select poly(A)-containing RNAs in rat hippocampus following treatment with CORT that are mediated by low-affinity glucocorticoid receptors. To determine if these responses are hippocampal specific, we examined RNA responses to glucocorticoids in several brain regions, myocardium, and cultured astrocytes by two-dimensional gel electrophoretic resolution of 35S-methionine labelled, in vitro translation products. RNAs coding for similar 35-, 33-, and 20-kdalton polypeptides are induced after 3 days of CORT treatment (40 mg/kg/day) in hippocampus, hypothalamus, cortex, striatum, cerebellum, and myocardium. Primary astrocyte cultures (neonatal rat), however, showed increases after hydrocortisone (1 µg/ml) in only the 20- and 33-kdalton translation products, while the 35-kdalton polypeptide was not detected. The hippocampal responses were maintained for up to 3 months during chronic daily CORT treatment. To determine if an increase in endogenous CORT levels would also evoke the RNA responses, we subjected rats to 2 h of vibratory stress and analyzed the in vitro translation products. RNAs coding for the 35- and 20-kdalton polypeptides were increased 3- to 5-fold in the hippocampus after acute stress in intact rats, but not in stressed adrenalectomized rats. These results suggest a new class of molecular stress responses in brain cells that is glucocorticoid dependent under physiological conditions