Sustained decrease in fat consumption produced by amphetamine in rats maintained on a dietary self-selection regime

Total daily caloric intakes and dietary self-selection of the three macronutrients, protein, fat and carbohydrate, were examined in female rats following the administration of anorectic doses of d-amphetamine sulfate (0.5, 1.0 and 2.0 mg/kg body weight, IP). Animals had access to nutrients for a six-hour period each day with food intakes measured two hours after food presentation and again at the end of the six-hour feeding period. Amphetamine injections led to similar dose-related decreases in caloric intakes in animals maintained on a standard laboratory diet (ground Purina Laboratory Chow) and those maintained on the dietary self-selection regime. Detailed examination of feeding patterns of animals given the self-selection regime revealed, however, that amphetamine had differential effects on the consumption of protein, fat and carbohydrate. At all three drug doses, protein and carbohydrate intakes were suppressed during the initial two-hour measurement period. Intakes of these two macronutrients returned to control values by the end of the six-hour feeding period. In contrast, fat intake was initially suppressed and remained suppressed throughout the entire six-hour period following amphetamine administration. Comparison of the present results with those of previous experiments indicates that the selective effect of amphetamine on fat consumption is not a general effect of drugs which reduce caloric intake.