The occurrence of tolerance to a central depressant effect of nicotine

1. Rats were injected with 0.8 mg nicotine/kg, 0.8 mg amphetamine/kg or with saline immediately before being tested for 30 min in activity boxes.2. During the first 3 trials the nicotine group were less active than the controls but from trial 5 onwards nicotine had a stimulant effect. The stimulant effect of the amphetamine did not alter with repeated injection.