Effects of amphetamine, dexfenfluramine, diazepam, and dietary manipulations on responding reinforced by stimuli paired with food in nonhuman primates.

The purpose of this study was to determine how stimuli paired with food alters the effects of pharmacological and dietary manipulations on food intake. Responding of baboons was studied using a schedule of reinforcement that simulated food 'seeking' and food 'taking'. Under one condition, responding during the initial seeking component was reinforced by flashing lights that were paired with food delivery during the latter-taking component. Under another condition, responding during seeking components was reinforced by a 1-s time out that was paired with food delivery during the latter-taking component. Dexfenfluramine (DFEN) decreased responding within seeking and taking components under both conditions. Diazepam (DZP) increased responding within seeking and taking components under both conditions. Amphetamine (AMPH) increased responding within seeking components under the flashing-light condition, but did not alter responding within seeking components under the 1-s time-out condition. AMPH decreased responding within taking components under both conditions. As observed with AMPH, caloric prefeeding also increased responding within seeking components only under the flashing-light condition. As observed with DZP, acute deprivation also increased responding within seeking and taking components under both conditions. The effects of AMPH and caloric prefeeding on food seeking are dependent upon the type of stimuli, paired with primary reinforcement.