The contribution of adrenal and reproductive hormones to the opposing effects of stress on trace conditioning in males versus females.

Exposure to an acute stressful experience facilitates classical conditioning in male rats but impairs conditioning in female rats (T. J. Shors, C. Lewczyk, M. Paczynski, P. R. Mathew, & J. Pickett, 1998; G. E. Wood & T. J. Shors, 1998). The authors report that these effects extend to performance on the hippocampal-dependent task of trace conditioning. The stress-induced impairment of conditioning in females was evident immediately, 24 hr and 48 hr after stress, depending on the stage of estrus. Moreover, the effect could be reactivated days later by reexposure to the stressful context. Corticosterone levels correlated with overall performance in males but not in females. Unlike the effect seen in males, adrenalectomy did not prevent the stress-induced effect on conditioning in females. These data indicate that exposure to the same experience can have opposite effects on learning in males versus females and that these opposing effects are mediated by differing hormonal systems.