Rapid Discrimination of Rewarding Nutrient by the Upper Gastrointestinal Tract

Abstract

When certain nutrients are injected into the stomachs of rats that are drinking one of two samples of nonnutrient, flavored water, the rats will (within a 10-minute session) choose the flavor paired with the nutrient. Such rewarding effects have obtained with predigested milk but not with similarly treated glucose or fresh milk. The results suggest the presence of rapidly acting, specialized, nutrient receptors in the upper gastrointestinal tract.