Captopril as an antidepressant? Effects on the learned helplessness paradigm in rats.

Several clinical investigations have suggested that captopril, an angiotensin-converting enzyme inhibitor (ACEI), currently used as an antihypertensive agent, exhibited anti-depressant properties in humans. The present experiment was evaluated for potential antidepressive activity of captopril on the learned helplessness paradigm in rats. Captopril (8, 16, 32 mg/kg/day, IP) induced a reversal of escape deficits but did not affect significantly the motor activity, suggesting that this effect was not due to motor stimulation. This antidepressant-like activity was comparable to that of imipramine (16, 32 mg/kg/day, IP). Naloxone (0.5; 1 mg/kg, IP) blocked the effect of captopril (16 mg/kg, IP) in this test. These results suggest that an opioid mediation could be responsible at least in part for its behavioral effect.