Effects of oral and intestinal stimulation with umami substance on gastric vagus activity.

Oral or intestinal stimulation with isotonic MSG solution caused an increase in discharge rate of the gastric branch of the vagus nerve. However, stimulation with physiological saline was without effect. The observations indicate that the oral or intestinal administration of MSG stimulates taste receptors in the tongue or amino acid receptors (MSG receptors) in the intestine which results in activation of the gastric branch of the vagus nerve, and explain the mechanism of reflex activation of gastric function originated by the ingestion of umami substance such as MSG.