Interactive effects of caffeine, 2-chloroadenosine and haloperidol on activity, social investigation and play fighting of juvenile rats.

The effects of caffeine, 2-chloroadenosine and haloperidol and their interaction on activity, social investigation, and two measures of play fighting (crossover and pinning), were investigated in juvenile male rats. Caffeine (20 mg/kg) increased activity, decreased crossover and pinning, but had no effect on social investigation. Both 2-chloroadenosine (0-10 mg/kg) and haloperidol (0-10 mg/kg) depressed activity, social investigation, crossover and pinning. When given together in varying dosages, caffeine and 2-chloroadenosine had behavioral effects suggestive of a competitive interaction between the two drugs. In contrast, the effects of haloperidol were not appreciably altered by simultaneous caffeine treatment. These results suggest that the influence of caffeine and 2-chloroadenosine on activity, social investigation and play fighting involve interaction with adenosine receptors.