Agonistic behavior during stress prevents the development of learned helplessness in rats.

Male Wistar rats were subjected to unavoidable electrical pain stimulation either in individual cages or in pairs. During the procedure, rats stressed in pairs fought. After 48 h, rats were tested in a shuttle box for the ability to develop active avoidance responses. The proportion of escape and avoidance responses was significantly lower in rats stressed individually as compared with intact animals and animals stressed in pairs. Plasma corticosterone was assayed one day later, at rest and after dexamethasone administration. There were no significant differences in resting corticosterone level between groups of animals. Administration of dexamethasone significantly reduced the plasma corticosterone level in intact rats and in animals stressed in pairs, but not in rats stressed individually. Thus, agonistic behavior during unavoidable stress prevents the development of pathological changes in adaptive behavior and the endocrine system.