Effect of (+)- or (-)-enantiomers of fenfluramine or norfenfluramine on nutrient selection by rats.

Abstract

The effects of the (+)- and (-)-enantiomers of fenfluramine and norfenfluramine on food choice and total food consumption by rats, have been examined. Animals were trained to select their food during an 8-h daily interval from two isocaloric-isocarbohydrate (40%) diets differing in protein contents (5 or 45% casein). Low doses of (+)-fenfluramine (1.25 or 1.65 mg kg-1) selectively reduced consumption of the 5%-protein diet during the hour after administration, thereby also reducing carbohydrate intake by a greater proportion than protein intake. Higher doses (2.5 or 4.0 mg kg-1) diminished consumption of both test diets to an equivalent extent. (+)-Norfenfluramine, although anorectic, did not modify the relative consumptions of carbohydrate and protein at any dose tested. These observations affirm that nutrient selection as well as total food consumption can be altered by drugs affecting particular neurotransmitters.