Postingestive modulation of the sweetness preference gradient in the rat.

Preference for a solution of a particular sweetness is increased by its previous association with postingestive effects of 10% glucose or polysaccharide solutions. Sweetness acceptance is decreased by previous association with 25%-50% glucose solutions. Conditioning in these two directions simultaneously by continuous access to a choice of solutions can reverse the usual gradient of preference for the sweeter of two solutions. This reversal is initially facilitated, but after some days attenuated, by a high proportion of carbohydrate in the diet. The reversal extinguishes over a few days without reinforcement. Expression of the relative aversion to the sweeter solution is not dependent on immediately prior carbohydrate ingestion (unlike sickly taste in man). Such conditioned attractions and aversions may assist normal caloric regulation.