Effect of amphetamine on sucrose-reinforced lever pressing: interaction with food deprivation.

Rats were trained to lever press on a Fixed Ratio Schedule 8 using sucrose reinforcement in one of two feeding conditions: ad lib food and water available in the home cage; reduced feeding in order to maintain the animals at 80% of their free feeding body weight. The effect of three doses of d-amphetamine (0.10, 0.25 and 0.50 mg/kg) on lever pressing was examined for each feeding condition. A systematic decrease in responding as dose increased was found in the ad lib feeding condition while only the highest dose had any effect on responding in the food restricted animals. Thus, it appeared that the effect of food deprivation was to shift the amphetamine dose-response curve to the right.