The effect of chronic self-administration of d-amphetamine on food intake, locomotor activity, and C14-leucine incorporation into cerebral cortex protein.

Rats had free access to 0.02% d-amphetamine solution instead of water for 23 days. The daily amphetamine consumption was found to increase from 16 mg/kg on day 1 up to 47 mg/kg on day 23. Tolerance to the anorexic effect of the drug was apparent on day 11. The initial depression in body weight persisted throughout the experiment. The hyperactivity of rats remained at the same level despite the daily increase in amphetamine intake. The incorporation of C14-leucine into cerebral cortex proteins was initially increased and returned to control level after 2 weeks of treatment. No direct correlation between hyperactivity and brain cortex protein synthesis was observed.