A presynaptic site of action of substance P and vasoactive intestinal polypeptide on myenteric neurons

Substance P, vasoactive intestinal polypeptide, potassium and veratrine stimulated release of acetylcholine from isolated myenteric varicosities of guinea pig small intestine. Only the effect of veratrine was blocked by tetrodotoxin. The neuronal topography and action of these neuropeptides indicate a major cholinergic modulatory role for them in the myenteric plexus.