Potentiation of cocaine's discriminative effects by caffeine: a time-effect analysis

The effects of caffeine upon the discriminative and rate-altering effects of cocaine were examined in rats. Using a food-reinforced two-lever operant procedure, 12 male Sprague-Dawley rats were trained to discriminate between 10 mg/kg cocaine and saline. Time-effect analysis of the training dose resulted in a median effective time interval (the duration of the discriminable effects of cocaine in producing 50% cocaine-appropriate responding), of 60.5 minutes postinjection. Caffeine partially generalized to the cocaine stimulus and, when administered with cocaine, produced a dose- and time-dependent increase in the percentage of drug-appropriate responding. Data are discussed with reference to our previous results with cocaine-caffeine interactions.