The CS–US delay gradient in flavor preference conditioning with intragastric carbohydrate infusions

Abstract

Rats are able to associate a flavor with the delayed presentation of a food, but the obtained flavor preferences are often weak. The present studies evaluated the effect of delay between a flavor CS and a post-oral nutrient US on the expression of conditioned flavor preferences. In Experiment 1, rats were trained with two CS flavors: one was followed after a delay by intragastric infusion of 8% glucose, and the other was followed after the same delay by intragastric water. Rats trained with 2.5, 10, and 30-min delays expressed significant (84 – 68%) preferences for the glucose-paired flavor whereas rats trained with 60-min delays were in different (51%). Experiment 2 examined flavor conditioning over a 60-min delay using 8 or 16% Polycose based on findings that orally consumed Polycose conditions preferences at this delay interval. The 8 and 16% Polycose infusions produced significant preferences which peaked at 62% and 73%, respectively. The ability to bridge these delays may allow animals to learn about slowly digested foods.

Nutrient-conditioned intake stimulation does not require a distinctive flavor cue in rats

“…While glucose rather than maltodextrin infusions were used in these studies, published data indicate that intestinally infused maltodextrin is rapidly digested to glucose and is as rapidly absorbed as infused glucose (Daum et al, 1978). Furthermore, IG glucose and maltodextrin infusions condition comparable flavor preferences in rats (Ackroff et al, 2012;Sclafani et al, 1993;Sclafani & Nissenbaum, 1988). Rather than the form of glucose infused, differences in the flavor of the oral stimulus appear to account for different intake stimulatory effects observed in the present and prior studies.…”

Rapid post-oral stimulation of intake and flavor conditioning by glucose and fat in the mouse

“…3-9 and 11. In tests 2 and 3 the mice licked more glucose than sucralose in bins [1][2][3][4][5]7, and 9 and in bins 1-4, and 6 -7, respectively. A comparison of the 3-min bin data from the capsaicin and control groups revealed no significant group differences in tests 0, 2, and 3.…”

Role of gut nutrient sensing in stimulating appetite and conditioning food preferences

“…Thus the animal controls the amount and timing of the infusion, which mixes with the consumed CS solution in the stomach and empties normally into the intestines. Flavor preferences are also conditioned by fixed-volume IG infusions that begin as the animal starts licking the CS solution or with a delay up to 1 h after the animal has ended its CS drinking session (2). Thus, as in the case of flavor aversion learning (87), animals can learn to prefer a flavor paired with immediate as well as delayed postoral nutrient feedback.…”