Lack of effect of corticosterone administration on male sexual behavior of rats

The increase in plasma levels of corticosteroids as part of the stress response has been associated with failure in the reproductive function in most vertebrate species, both in females and males. Recently, we have shown that male sexual performance in rats is readily affected by different stressors, both acutely and chronically applied. However, there are few reports that directly correlate the increase in corticosteroid levels with the behavioral effects of stress. In this study we investigated whether the administration of corticosterone, either acutely or chronically, could reproduce the effects of stress on male sexual behavior in the male rat. Four doses of corticosterone (0.5, 1, 2, and 4 mg) or the vehicle, were administered during four consecutive days to sexually experienced males. Male sexual behavior was assessed after the first and the fourth injection. After the last test, males were killed and levels of corticosterone and testosterone were measured by HPLC. We observed an increase in corticosterone plasma levels in a dose-dependent manner. None of the sexual behavior parameters, however, was modified. Plasma levels of testosterone were not modified by corticosterone administration. Both steroids were increased in response to sexual activity, though. These data show that, unlike amphibians and female mammals, corticosteroids do not alter sexual behavior in male rats and suggest that the effect of stress on male sexual behavior cannot be explained by increases in corticosterone.