Sham feeding in rats after ventromedial hypothalamic lesions and vagotomy.

Sham feeding was examined in female rats with ventromedial hypothalamic (VMH) lesions with or without abdominal vagotomy. In Experiment 1, intact rats consumed more than twice as much sweet milk during 1-hr tests of sham feeding (M = 13.0 ml) as they did when feeding normally (M = 5.5 ml). Rats with VMH lesions showed exaggerated sham feeding, which was elevated almost fourfold (M = 56.6 ml) over their already high normal feeding baseline (M = 15.1 ml). In Experiment 2, vagotomy substantially reduced sham feeding in rats with VMH lesions. After vagotomy, VMH rats sham fed half as much (M = 23.7 ml) as nonvagotomized VMH rats did (M = 46.8 ml). Vagotomy did not, however, reduce sham feeding to control levels (M = 13.1 ml). These results are consistent with the hypothesis that VMH hyperphagia arises from exaggeration of orosensory responsiveness, which is, in part, a consequence of perturbed vagal function.