The effects of d-amphetamine on the reinforcing effects of food and fluid using a novel procedure combining self-administration and location preference.

Using a laboratory animal procedure designed to measure two aspects of behavior related to commodity seeking (self-administration and location preference), five individually housed adult rhesus monkeys lived in three chambers: fluid- (sweetened Kool-Aid solution) related cues and oral fluid self-administration were specific to one end chamber, food pellet-related cues and food self-administration were specific to the other end chamber, and no food cues or fluid cues were available in the middle chamber. Throughout the 10 h experimental day, monkeys experienced multiple food, fluid, choice (food versus fluid), and no-commodity sessions. Oral d-amphetamine (AMPH; 0.5-1.5 mg/kg) or placebo was administered before the sessions to determine if this anorectic drug would differentially alter food and fluid self-administration. The effects of AMPH on the length of time monkeys spent in each chamber, when the stimulus lights indicating commodity availability were not illuminated (location preference) were also determined. AMPH decreased both food and fluid self-administration, but responding for fluid was reduced to a greater extent than responding for food. AMPH, however, increased the length of time monkeys spent in the food chamber, even when no stimulus lights indicating food availability were illuminated. The increase in the length of time spent in the food chamber was predicted by the decrease in the number of fluid deliveries, not the number of food deliveries. These results indicate that the relationship between self-administration and location preference, as measures of reinforcing effects, is not completely concordant. The current procedure may prove useful in comparing these two measures of reinforcing effects with other reinforcers.