Failure of dexamethasone to influence sex differences in acquisition of discriminated lever press avoidance

Discriminated lever press avoidance was used to test the hypothesis that higher plasma levels of pituitary-adrenocortical hormones in female rats can be held responsible for the superior active avoidance of female as compared to male rats. Male and female rats were administered dexamethasone (500 microg/kg body weight) during 4 days of avoidance acquisition and 1 additional day of extinction. This treatment resulted in a strong suppression of the pituitary-adrenocortical activity in both sexes. The corticosterone plasma level was very low, the adrenal weight was significantly reduced, but the pituitary weight was not affected. In other words, animals treated with dexamethasone were exposed to the lever press avoidance situation without a reactive pituitary-adrenocortical system. Under these conditions, sex differences in behavior were not affected and, therefore, the hypothesis that sex differences in pituitary-adrenocortical hormone levels contribute to sex differences in active avoidance, was not confirmed.