Fenfluramine and amphetamine suppress dietary intake without affecting learned preferences for protein or carbohydrate cues.

The effects of pharmacological modulation of monoamine transmitter activity on genuine nutrient selection were assessed: that is, drug-induced changes in nutrient-specific dietary choice behaviour were measured, using rats that had learned to select an odour cueing protein content or carbohydrate content of the diet. Anorexigenic doses of DL-fenfluramine-HCl (1.25 or 2.5 mg/kg) and D-amphetamine2 SO4 (0.5 or 1.0 mg/kg) did not affect the selection of protein-paired or carbohydrate-paired odours by trained rats. This weighs against the claim that 5-hydroxytryptamine or catecholamine transmitters are involved in the selection of macronutrients, as distinct from selection between diets in response to sensory differences functionally unrelated to nutrient composition.