The effects of subdiaphragmatic vagotomy in rats with ventromedial hypothalamic obesity

The present study investigated the effects of subdiaphragmatic vagotomy in rats with ventromedial hypothalamic (VMH) lesions and obesity. Vagotomy or sham-vagotomy was performed two weeks after VMH lesions and rats were observed for 4 more weeks. Complete vagotomy reversed the VMH obesity, lowered serum insulin, lowered basal gastric acid and blocked the secretion of gastric acid after stimulation of the cervical vagus. Pair-feeding of VMH-lesioned rats without vagotomy to the food intake of vagotomized animals also reversed the obesity, lowered serum insulin and lowered basal acid secretion, but it did not prevent the rise in acid after vagal stimulation. These results suggest that subdiaphragmatic vagotomy reversed the obesity of VMH lesioned rats primarily by decreasing food intake. However, there was a positive correlation (r = .70) between the level of serum insulin and basal gastric acid in VMH lesioned rats which remained significant when the effects of food intake were held constant (partial correlation coefficient = 0.449). This supports the possibility that ventromedial hypothalamic injury is followed by enhanced vagal activity and that the vagus may play an important part in the hyperinsulinemia of VMH obesity.