Vagotomy blocks hypothalamic hyperphagia in rats on a chow diet and sucrose solution, but not on a palatable mixed diet.

Adult female rats were given ventromedial hypothalamic parasagittal knife cuts (VMH treatment) or control surgery (Con treatment), followed 10 days later by subdiaphragmatic vagotomy (Vag treatment) or sham vagotomy (Sham treatment). The hyperphagia and obesity produced by the VMH cuts to rats on a chow diet was completely blocked by vagotomy (VMH-Vag group). Vagotomy also inhibited the VMH rats' overconsumption of a 20% sucrose solution during 1 hr/day and 24 hr/day tests, which contrasts with the effects of atropine treatment. However, when offered a selection of palatable foods (cookies, sweet milk, high-fat ration) in addition to chow, the VMH-Vag rats overate and gained considerably more weight than did the Con-Vag rats or the Con-Sham rats. The Con-Vag rats, on the other hand, gained less weight than did the Con-Sham rats on the palatable diet. The results indicate that intact subdiaphragmatic vagi are not essential for the expression of VMH hyperphagia and finickiness, and they therefore question the role of vagally mediated cephalic responses in the hypothalamic hyperphagia syndrome. On the other hand, the results indicate that in brain-intact animals vagotomy suppresses the development of diet-induced obesity.