Effects of caffeine on DRL performance in the mouse.

Mice were trained to stable and efficient DRL 18 sec performance utilizing a nose-poke as the operant. Caffeine, at doses less than 48 mg/kg, increased both response bursts (IRTs less than 3 sec) and longer IRTs, and shifted the IRT distribution towards shorter, nonreinforced IRTs. Auditory feedback for responses decreased the number of bursts emitted and produced performance more resistant to drug effects. These results are similar to those previously reported for caffeine on DRL in the rat, and for amphetamine on DRL in a variety of species.