Factors influencing tolerance to d-amphetamine-induced anorexia in rats.

Three experiments were concerned with tolerance to anorexia induced by d-amphetamine. In experiment 1, one group of rats on a 2 hr food deprivation schedule received 2 mg/kg of d-amphetamine 15 min before eating every other day for a month. A second group of rats on a similar schedule received the same dose of d-amphetamine immediately after eating. When compared to a saline-treated control group, the former group showed significant decreases in weight and food intake; tolerance to the amphetamine-induced anorexia began to occur toward the end of the experiment. The latter group showed a significant decrease in food intake on the non-drug days and an overall weight loss when compared to the control group. Experiment 2 demonstrated that tolerance to d-amphetamine-anorexia was related to the duration of drug administration per se. Experiment 3 showed that taste can be a factor in influencing the rate of tolerance to d-amphetamine-induced anorexia. These results indicate that both pharmacological and experiential factors play an important role in determining the rate of tolerance to this action of d-amphetamine.