Increased flavor acceptance and preference conditioned by the postingestive actions of glucose

In Experiment 1, rats were given daily 2-h access to chow and water and 20-h access to flavored solutions (cherry or grape). On alternate days, one flavor (CS+) was paired with intragastric infusions of 16% glucose and another flavor (CS-) with IG water. In subsequent choice tests, the rats strongly preferred (95%) the CS+ to the CS-. CS+ intake also greatly exceeded CS- intake during one-bottle training sessions (71 vs. 18 g/20 h). This increased acceptance was due to both increased bout size and number. When CS+ was paired with IG water (extinction test), CS+ bout size declined to CS- levels, while CS+ bout number and total intake remained elevated. In Experiment 2, rats trained with sucrose octa acetate and citric acid solutions also showed increased CS+ acceptance and preference in one- and two-bottle tests, respectively. The rats also consumed more CS+ than CS- during short-term (30 min/day) one-bottle tests and intraoral intake tests under both deprived and ad lib. feeding conditions. These results demonstrate that the postingestive actions of glucose can condition substantial increases in flavor acceptance as well as flavor preference.