Food deprivation enhances the expression but not acquisition of flavor acceptance conditioning in rats.

The postingestive actions of nutrients condition strong flavor preferences in rats and may also enhance flavor acceptance (increase total intake) in some situations. This study determined the impact of food deprivation on flavor preference and acceptance conditioned by intragastric (i.g.) infusions of glucose. Rats fitted with gastric catheters were trained (20 h/day) to associate a CS+ solution (bitter or sour) with i.g. 16% glucose and a CS- solution with water infusions. One group (FR) was food-restricted during the training sessions, while a second group (AL) was given food ad libitum. All rats were given 2-h access to food prior to the daily sessions. During one-bottle training, the FR rats consumed substantially more CS+ than CS- whereas AL rats drank only slightly more CS+ than CS-. In additional one-bottle acceptance tests, the FR and AL rats consumed substantially more CS+ than CS- when both groups were food-restricted, but only slightly more CS+ than CS- when both groups had food ad libitum. Throughout the experiment, the FR and AL rats displayed equally strong CS+ preferences in two-bottle choice tests irrespective of their deprivation state during the test. The findings indicate that food restriction stimulates the intake of a CS+ flavor that is (or was previously) paired with i.g. glucose infusions but does not fundamentally alter the learned association between the CS+ flavor and the post-oral nutrient stimulus.