Aversive behavior during intraoral intake in male rats

We investigated if the taste of a sucrose solution becomes progressively mo re aversive during intraoral infusion and if this contributes to the termin ation of the intake in male rats. The display of aversive behavior, such as gapes and chin rubs, but not headshakes, forelimb flails or orofacial groo ming, varied with the concentration of an intraorally infused solution of q uinine hydrochloride (QHCl) and increased by the time the rat rejected an i ntraorally infused 2 M solution of sucrose. Activation of gapes and chin ru bs by brief intraoral infusion of QHCl advanced the rejection of the sucros e solution if given late during intraoral infusion, but blockade of gaping by anaesthesization of the oral cavity with Xylocain did not prolong the in take of the sucrose solution. Headshakes and forelimb flails could be elici ted by stimulating the head and limbs with sucrose, and gapes and chin rubs were activated by infusion of a 2 M solution of sucrose into the stomach o r duodenum but not by infusion of glucose into the jugular or hepatic porta l vein. Preventing filling of the gastrointestinal tract during intraoral i nfusion of sucrose (sham feeding) eliminated the display of gapes and chin rubs. It is suggested that an increase in the aversiveness of the taste of a sucrose solution contributes to the rejection of that solution during int raoral infusion. However, rats can reject a sucrose solution in the absence of any behavioral sign of aversion and none of the so-called "taste-relate d" aversive behaviors is exclusively dependent upon stimulation of the tast e receptors in the oral cavity, (C) 2001 Elsevier Science Inc. All rights r eserved.