CARBOHYDRATE, FAT, AND PROTEIN CONDITION SIMILAR FLAVOR PREFERENCES IN RATS USING AN ORAL-DELAY PROCEDURE

Flavor preferences conditioned by carbohydrate (Polycose), protein (casein hydrolysate), and fat (corn oil) were compared using an oral-delay training method. In Experiment 1 separate groups of food deprived rats were trained to associate a CS+ flavor (e.g., grape-saccharin) with the delayed (10 min) presentation of isocaloric carbohydrate, protein, or fat sources. A CS- flavor (e.g., cherry-saccharin) was paired with the delayed presentation of an unflavored saccharin solution. In subsequent two-bottle tests the carbohydrate, protein, and fat trained groups displayed significant preferences for the CS+ over the CS-. In Experiment 2 each rat was trained to associate two new flavors with two of the three nutrients (e.g., orange with carbohydrate, and strawberry with protein). In subsequent two-bottle tests the rats equally preferred the two nutrient-paired flavors. Experiment 3 compared the preferences for the new CS+ flavors vs. the original CS- flavor. The rats displayed similar preferences for carbohydrate-, protein- and fat-paired CS+ over the CS-. The similar preferences obtained with the three different nutrients support the view that preference conditioning is mediated by the nutrients' caloric value. Other studies suggest, however, that nutrient specific signals are also involved in the conditioning process.