The acquired control of ingestive behavior in the rat by flavor-associated postingestional stimulation

Recently reported sham feeding studies have revealed that the rate of ingestion of liquid diets early in the ingestion interval is under the associative control of postingestive events occurring in the stomach and intestine. This study investigated the possibility that gastrointestinal filling induced by adding the nonabsorbable sugar alcohol mannitol to a test solution could serve as an unconditioned stimulus to support the acquired control of the initial rate of ingestion of a liquid by rats. The results revealed that mannitol had a direct unconditioned effect on the rate of decline in the rate of ingestion during the meal and that the association of it with a distinctive flavor resulted in an acquired control of the initial rate of licking conditioned to the flavor. The conditioned effect was rapidly acquired and rapidly extinguished. Our results demonstrate the preabsorptive mechano- or chemostimulation of the gastrointestinal tract can serve as a UCS to support the conditioning of the rate of ingestion early in the meal.