Eplerenone, a selective mineralocorticoid receptor blocker, exerts anxiolytic effects accompanied by changes in stress hormone release.

The aim of this study was to investigate the impact of chronic treatment with eplerenone, a mineralocorticoid receptor antagonist and clinically used antihypertensive drug, on animal correlates of mood disorders, namely anxiety-like behaviour, stress hormones release and brain plasticity. Male rats (n = 40) were injected subcutaneously twice daily with eplerenone (50 mg/kg body weight) or vehicle for 11 days. Open-field and elevated plus-maze tests were used as both anxiety-related paradigms and stress stimuli to evaluate hormone responses. Eplerenone-treated rats showed reduced anxiety-like behaviour manifested by both conventional and ethological parameters related to exploration and risk assessment behaviour in the elevated plus-maze test and partially in the open-field test. Eplerenone treatment resulted in an elevation of plasma aldosterone and oxytocin levels. Chronic treatment with eplerenone prevented the stress-induced rise in plasma corticosterone levels and vasopressin concentrations in the posterior pituitary. Eplerenone treatment failed to induce substantial changes in hippocampal brain derived neurotrophic factor protein concentrations. In conclusions, chronic treatment with eplerenone (1) exerts anxiolytic effects and (2) influences corticosterone, oxytocin and vasopressin concentrations in a manner consistent with the anxiolytic outcome.