Testosterone dependent effects of caffeine on social investigation by adult male rats.

The testosterone determinants of caffeine induced increases in locomotor activity and social investigation by adult rats was investigated. In all groups where testosterone levels were high (intact or sham castrate adult males or castrate males receiving testosterone replacement) caffeine increased the social investigation of a novel juvenile rat. In condition where androgen levels were low (adult females, castrate males and castrate males receiving oil injections) social investigation was not affected by caffeine. In contrast, locomotor activity was increased by caffeine in all treatment groups. Thus, testosterone has behaviorally specific effects on the caffeine responsiveness of the rat.