FLAVOR PREFERENCES CONDITIONED BY INTRAGASTRIC POLYCOSE IN RATS - MORE CONCENTRATED POLYCOSE IS NOT ALWAYS MORE REINFORCING

Prior studies have obtained conditioned preferences for flavors paired with intragastric (IG) infusions of Polycose (hydrolyzed starch) at c oncentrations of 1-32% over a different flavor paired with IG water. T he present study determined if rats would also learn to prefer a flavo r paired with concentrated Polycose infusion over a flavor paired with a more dilute Polycose infusion. In Experiment 1, adult female rats w ere food-deprived and trained during alternating one-bottle sessions ( 30 min/day) to associate one flavored solution (the CS+8) with IG infu sions of 8% Polycose, a second flavored solution (the CS+16) with IG i nfusions of 16% Polycose, and a third flavored solution (the CS-) with IG water infusions. In subsequent choice tests, the rats displayed si milar preferences for the CS+8 and CS+16 over the CS-, but preferred t he CS+16 to CS+8 in a direct choice test. A similar preference pattern was obtained in 22 h/day tests with the rats nondeprived. In Experime nt 2, new rats were similarly trained and tested but with CS+16 and CS +32 solutions paired with 16% and 32% Polycose infusions, respectively . The rats preferred both CS+ solutions over the CS- solution in the s hea-and long-term tests. However, the CS+16 was preferred over the CS32 by the food-deprived rats in the short-term tests. The two CS+ solu tions were equally preferred in the long-term tests with food ad lib. These and other findings indicate that the postingestive reinforcing a ction of Polycose increases as concentration increases from 1% to 16% but does not increase further, and may actually decrease, at a 32% con centration. The rapid satiating effect of concentrated carbohydrate so lutions may limit their reinforcing consequences. (C) 1998 Elsevier Sc ience Inc.