Effects of corticosterone on response consolidation and retrieval in the forced swim test.

In the forced swimming test, adrenal hormones regulate immobility time during a test swim given 24 hr after the initial training swim (e.g., the deficit in adrenalectomized animals is reduced when animals are given corticosterone [B] immediately after the training session). In this study, adrenalectomy decreased and B restored immobility during the test swims. The effects of adrenalectomy were completely reversed by 1 mg/kg doses of B, which results in plasma B levels that are comparable to values under basal resting conditions. Higher doses of B had no further effect. B given before or immediately after training partially reversed the effects of adrenalectomy. The complete reversal of the effects of adrenalectomy, however, required the presence of B during both training and testing, suggesting that B plays a role in the consolidation-retention and retrieval of the immobility response.