Postingestive alliesthesia: the rat tells the same story

Facial consummatory responses reflecting ingestive and aversive perceptions were studied and quantified in rats chronically implanted with gastric and oral catheters. A gustatory stimulus of 50 microliters of 0.6 mol.l-1 sucrose was injected into the mouth every 5 min during 60 min. At time zero, 5 ml of either 1.1 mol.l-1 glucose or water were injected into the stomach. The typical ingestive facial consummatory responses were observed in response to sweet stimuli prior to all gastric loads, and after the water loads. On the other hand, the aversive consummatory responses were observed in response to sweet stimuli after glucose gastric loads. The reversal of the consummatory responses from ingestive to aversive was stronger with higher concentration of the gastric load, and relatively independent from the volume of the load or the amount of glucose injected intragastrically. These results in rats parallel human postingestive alliesthesia.