Testosterone plays a limited role in cocaine-induced conditioned place preference and locomotor activity in male rats.

Growing evidence suggests that sex differences in cocaine reward responses are regulated by endogenous gonadal hormones. However, few studies have addressed the role of testosterone on cocaine reward and psychomotor activation. This study aimed to determine whether testosterone influences the development of psychomotor and reward responses to cocaine. Castrated 8-week-old male Fisher rats received placebo or testosterone via Silastic capsules (1-3 capsules of 100% testosterone) or subcutaneous injections (400, 800, or 1200 microg/kg) concurrent with cocaine administration. Although chronic testosterone administration did not alter cocaine-induced conditioned place preference (CPP), concurrent administration of testosterone and cocaine affected the development of cocaine CPP dose-dependently; 400 microg/kg blocked the expression of cocaine-induced CPP. Testosterone did not affect cocaine-induced locomotor activity. Furthermore, testosterone-saline-treated controls did not develop CPP, suggesting that at these doses, testosterone does not produce rewarding or motor responses. These data suggest that testosterone may play a limited role in cocaine-induced reward associations and locomotor responses and thus has a limited effect in the previously reported sexually dimorphic responses to cocaine.