Flavor preferences conditioned by intragastric polycose infusions: a detailed analysis using an electronic esophagus preparation.

The present series of experiments examined the rat's conditioned preference for flavors associated with intragastric (IG) Polycose infusions. Adult female rats were fitted with two chronic intragastric catheters and were trained to drink flavored water (CS+; e.g., cherry-water) paired with IG infusions of 32% Polycose. On alternate days a different flavor (CS-; grape-water) was paired with IG water infusions. The flavored water and chow were available 23 hr/day. In subsequent two-choice tests the rats displayed strong preferences for the CS+ flavor (up to 98%). The CS+ preference persisted for several weeks during extinction tests when both the CS+ and CS- were paired with IG water or with no infusions. The rats also preferred the CS+ to plain water which contrasts with the mild aversion naive rats display to the flavored water. The acquired preference for the CS+ flavor was not as strong, however, as the rats' innate preferences for the taste of saccharin or Polycose. Also, unlike their response to saccharin and Polycose, the rats' acceptance (absolute intake) of the CS+ flavor was not elevated. CS+ intake was increased, though, when saccharin was added to the flavored water. The rats reversed their flavor preference when the reinforcement contingencies were reversed. Also, in the absence of unique flavor cues, the rats learned to prefer, apparently based on somatosensory cues, the sipper tube that was paired with IG Polycose infusions. The effects of flavor and IG Polycose infusions on drinking patterns and caloric intake are also described.