Vagotomy produces learned food aversions in the rat

Subdiaphragmatic vagotomy produces hypophagia and weight loss in normal rats and can reverse the hyperphagia and obesity of rats with ventromedial hypothalamic lesions. Vagotomy surgery can also produce symptoms of nausea and discomfort. Since such symptoms are highly effective as unconditioned stimuli in food aversion conditioning, the present studies examined whether some of the depression in food intake observed in rats with vagotomy could be due to the development of aversions to the foods eaten after their surgery. In the first study, significant aversions developed to the specific novel diet consumed after vagotomy, results indicating that the symptoms associated with vagotomy can serve as effective unconditioned stimuli in the acquisition of learned food aversions. The second study compared vagotomized animals consuming familiar laboratory chow with those consuming a novel diet. In contrast to the novel diets, learned aversions did not develop to the familiar chow, and hypophagia was less persistent and severe. It is concluded that learned food aversions can contribute to the appetite and weight loss exhibited by vagotomized animals. Consideration of the conditions under which these aversions arise after vagotomy surgery may allow for the design of studies so as to minimize the aversions and thereby separate these nonspecific effects from direct regulatory deficits produced by vagotomy.