Flavor Preferences Conditioned by Intragastric Polycose in Rats: More Concentrated Polycose Is Not Always More Reinforcing

Abstract

LUCAS, F., A. V. AZZARA AND A. SCLAFANI. Flavor preferences conditioned by intragastric Polycose in rats: More concentrated Polycose is not always preferred. PHYSIOL BEHAV 63(1) 7–14, 1998.—Prior studies have obtained conditioned preferences for flavors paired with intragastric (IG) infusions of Polycose (hydrolyzed starch) at concentrations of 1–32% over a different flavor paired with IG water. The present study determined if rats would also learn to prefer a flavor paired with concentrated Polycose infusion over a flavor paired with a more dilute Polycose infusion. In Experiment 1, adult female rats were food-deprived and trained during alternating one-bottle sessions (30 min/day) to associate one flavored solution (the CS+8) with IG infusions of 8% Polycose, a second flavored solution (the CS+16) with IG infusions of 16% Polycose, and a third flavored solution (the CS−) with IG water infusions. In subsequent choice tests, the rats displayed similar preferences for the CS+8 and CS+16 over the CS−, but preferred the 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 Experiment 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 short- and long-term tests. However, the CS+16 was preferred over the CS+32 by the food-deprived rats in the short-term tests. The two CS+ solutions were equally preferred in the long-term tests with food ad lib. These and other findings indicate that the postingestive reinforcing action of Polycose increases as concentration increases from 1% to 16% but does not increase further, and may actually decrease, at a 32% concentration. The rapid satiating effect of concentrated carbohydrate solutions may limit their reinforcing consequences.