Effects of amphetamine on food and fruit drink self-administration.

The effects of oral d-amphetamine (0.12-1.0 mg/kg) on the responding of adult baboons were examined during choice sessions. In Experiment 1, responding on 1 lever was reinforced with 1 food pellet, and responding on a 2nd lever was reinforced with 4 food pellets. The response requirement (fixed ratio [FR]) on the latter lever was 4 times the FR value; that is, the unit price (responses/g) was the same. Amphetamine decreased responding on both levers similarly under all conditions. In Experiment 2, responding on 1 lever was reinforced with 1 pellet, and responding on a 2nd lever was reinforced with a sweet fruit drink. Amphetamine decreased responding reinforced by food to the greatest extent when the FR value was large and fruit drink was available. Findings indicate that choice procedures can provide baselines that allow the evaluation of the specificity of a manipulation on intake of a commodity.