Electrical vagus nerve stimulation decreases food consumption and weight gain in rats fed a high-fat diet.

There is growing evidence that vagus nerve stimulation (VNS) has a suppressive effect on both short- and long-term feeding in animal models. We previously showed that long-term VNS (102 days) with low-frequency electrical impulses (0.05 Hz) decreased food intake and body weight in rats. In the present study, we investigated the effect of high frequency (10 Hz) VNS on feeding behavior and appetite in rats fed a high-fat diet; peptide secretion and other parameters were assessed as well. Adult male Wistar rats were each implanted subcutaneously with a microstimulator (MS) and fed a high-fat diet throughout the entire study period (42 days). The left vagus nerve was stimulated by rectangular electrical pulses (10 ms, 200 mV, 10 Hz, 12 h a day) generated by the MS. Body weight and food intake were measured each morning. At the end of the experimental period, animals were euthanized and blood samples were taken. Serum levels of ghrelin, leptin and nesfatin-1 were assessed using radioimmunoassays. Adipose tissue content was evaluated by weighing epididymal fat pads, which were incised at the time of sacrifice. To determine whether VNS activated the food-related areas of the brain, neuronal c-Fos induction in the nuclei of the solitary tract (NTS) was assessed. Chronic vagus nerve stimulation significantly decreased food intake, body weight gain and epididymal fat pad weight in animals that received VNS compared with control animals. Significant neuronal responses in the NTS were observed following VNS. Finally, serum concentrations of ghrelin were increased, while serum levels of leptin were decreased. Although not significant, serum nesfatin-1 levels were also elevated. These results support the theory that VNS leads to reductions in food intake, body weight gain and adipose tissue by increasing brain satiety signals conducted through the vagal afferents. VNS also evoked a feed-related hormonal response, including elevated blood concentrations of nesfatin-1.