Caffeine discrimination in the rat.

Rats were trained to discriminate 32 mg/kg caffeine from saline in a two-lever appetitive task. Across a range of caffeine test doses (1-32 mg/kg) rats showed a dose related generalization to the training cue. At intermediate caffeine dose levels, caffeine appeared to produce a more potent cue on tests following saline-training days than after drug-training days. Several psychomotor stimulants (d-amphetamine, methylphenidate, nicotine and TRH) failed to generalize to the caffeine cue. In contrast, theophylline did generalize to caffeine at a dose roughly twice that of the caffeine training dose.