Abdominal vagotomy does not block carbohydrate-conditioned flavor preferences in rats

The effects of abdominal vagotomy on the flavor preferences conditioned by Polycose (a maltodextrin) were investigated in female rats. Using an oral-delay training method, a modest conditioned flavor preference (67%) was obtained in control rats but not in rats with subtotal abdominal vagotomy (hepatic branch intact). The rats were fed a chow diet, and gastric stasis in the vagotomized rats may have interfered with preference learning. To facilitate conditioning, the rats were switched to a liquid maintenance diet and trained with new flavors paired with intragastric (IG) infusions of Polycose and water. With this procedure, the vagotomized and control rats acquired strong preferences (83-88%) for the flavor paired with IG Polycose. In a second experiment, flavor preferences conditioned by IG Polycose were obtained in rats with total abdominal vagotomy although the preference was attenuated relative to control rats (79% vs. 97%). Gastric motor problems (dumping) may have been a factor because the vagotomized rats consumed much less flavored solution (and therefore received less IG Polycose) during training than did controls. These findings indicate that an intact vagus nerve is not necessary to obtain carbohydrate-conditioned preferences, although vagotomy may interfere with the conditioning in some experimental situations.