Involvement of corticotropin-releasing factor subtype 1 receptor in the acquisition phase of learned helplessness in rats.

To determine if CRF receptor subtype 1 (CRF1) is involved in the acquisition phase of LH, we administered CRF receptor antagonists, CRA 1000 and CP-154,526, 60 min before (acquisition phase) or immediately after (consolidation phase) inescapable shocks on day 1, and 60 min before (retention phase) escape test on day 2. CRA1000 (10 mg/kg. p.o.) and CP-154,526 (30 mg/kg, p.o.) decreased the number of escape failures in the acquisition phase, but not in consolidation and retention phases. The tricyclic antidepressant, imipramine did not affect the number of escape failures in all 3 phases. Thus, the CRF1 receptor is apparently involved in the resultant escape failures in the acquisition phase of LH in rats.