Evidence for a role of capsaicin-sensitive mucosal afferent nerves in the regulation of mesenteric blood flow in the dog.

Capsaicin injected into the lumen of the small intestine produced marked changes in mesenteric blood flow in anesthetized dogs. In the majority of cases capsaicin evoked a significant increase in mesenteric blood flow, the time-course of which indicated it was of a reflex nature. The response to capsaicin was completely abolished by a previous intraluminal application of the local anesthetic lidocaine, and was inhibited by an intraarterial injection of somatostatin. The present findings suggest that the effects of capsaicin may be related to a release of vasoactive peptides from afferent nerves associated with the vascular system of the gastrointestinal tract. It is concluded that capsaicin-sensitive mucosal afferent nerves, possibly provided with an axon reflex arrangement, may play a role in the regulation of local intestinal blood flow.