Corticosterone attenuates conditioned fear responses and potentiates the expression of GABA-A receptor alpha-2 subunits in the brain structures of rats selected for high anxiety

The aim of the experiment was to assess the effects of an acutely administered corticosterone on the expression of GABA-A receptor alpha-2 subunits in the brain structures of high (HR) and low (LR) anxiety rats (divided according to their conditioned fear-induced freezing response) subjected to a second conditioned fear session (1 week after fear conditioning). We found that corticosterone (20 mg/kg, sc) given to rats prior to the second conditioned fear session significantly enhanced a decrease in fear expression in the HR group. The behavioural effect of fear was accompanied by the increased expression of alpha-2 subunits in the basolateral amygdala (BLA) and the dentate gyrus of the hippocampus (DG) of the HR group. Corticosterone potentiated the effect of fear on alpha-2 subunit expression in the BLA, DG, the cingulate cortex area 1 and the secondary motor cortex (areas Cg1 and M2). The current study provides insight into the mechanisms that may be responsible for the beneficial effects of glucocorticoids in the therapy of some anxiety disorders.

► Corticosterone decreased expression of conditioned fear in high anxiety rats (HR).
► Fear increased expression of alpha-2 subunits of GABA-A receptor in limbic structures.
► Corticosterone potentiated effects of conditioned fear on alpha-2 subunit expression.