Flavor preferences conditioned by intragastric nutrient infusions in rats fed chow or a cafeteria diet

Numerous studies demonstrate that chow-fed rats learn to prefer flavors that are associated with the postingestive effects of nutrients. The rats> limited dietary experience (i.e. only lab chow) may have facilitated preference learning because of the novelty of the training stimuli. This possibility was investigated by comparing nutrient conditioning in rats fed chow or a varied "cafeteria" diet. Rats in Experiment 1 were trained during alternate sessions (30 min/day) to drink two different flavors paired with concurrent intragastric infusions of 16% Polycose or water. Both diet groups displayed similarly strong preferences (89%) for and increased acceptance of the Polycose-paired flavor. A more demanding learning task was used in Experiment 2: new flavors were paired with delayed (15 min) infusions of Polycose or water. The chow and cafeteria groups both showed reduced, but comparable (78%, 77%) preferences for the Polycose-paired flavor. In Experiment 3, new flavors were paired with concurrent infusions of 7.1% corn oil or water. Again, the cafeteria and chow groups developed similar preferences for the nutrient-paired flavor (85%, 78%). Also, both groups preferred the Polycose-paired flavor of Experiment 1 to the oil-paired flavor of Experiment 3 (76%, 78%). These results indicate that dietary variety does not interfere with nutrient-conditioned flavor preference learning in rats.