Rapid corticosterone-induced changes in gene expression in rat hippocampus display type II glucocorticoid receptor...

Corticosteroids influence a wide range of neuronal activities by binding to either of two different glucocorticoid receptors found in rat brain. To investigate genomic responses in brain to stress levels of circulating corticosterone (CORT), we isolated hippocampal total RNA and poly(A)-containing RNA from rats treated with 10 mg/day CORT or vehicle. RNA translation products were resolved by 2-dimensional gel electrophoresis and fluorography. Select changes in four translation products after acute CORT treatment were inferred from up to 100-fold increases in three polypeptides and a 2-fold decrease in another. While adrenalectomy decreased levels of the inducible RNA sequences (adrenalectomized vs. intact controls), CORT increased the inducible sequences above their levels in intact controls. Rapid increases within 2 h of CORT treatment were seen for RNAs coding for 35, 33, and 20 kilodalton polypeptides. However, RNA coding for a 50 kilodalton polypeptide had a delayed decrease, first seen after 32 h CORT. The CORT increases displayed type II glucocorticoid receptor-specificity: RU 28362 greater than or equal to CORT greater than aldosterone greater than dihydrotestosterone = control. Since type II receptors are only substantially occupied by stress levels of CORT, these changes in gene expression are candidates for molecular stress responses in the brain.