Role of capsaicin-sensitive neurons in the control of intestinal blood flow and oxygen uptake.

The effects of periarterial placement of capsaicin upon intestinal blood flow, oxygen consumption and distribution of blood flow to the vascular compartments of the gut wall were measured in anesthetized dogs. Total blood flow to the segment of distal ileum was measured with an ultrasonic blood flowmeter and arteriovenous oxygen difference (AVO2) across the intestinal segment was determined spectrophotometrically. Intestinal oxygen uptake was calculated as the product of AVO2 and intestinal blood flow. Intestinal mucosal blood flow was also measured by laser-Doppler flowmeter. Changes in blood flow distribution were estimated from the distribution of radiolabeled microspheres. Capsaicin applied periarterially induced early increase in intestinal blood flow, oxygen uptake and increase in mucosal blood flow which was higher then increase in total blood flow. The acute capsaicin-induced vascular dilation was followed by steady state response characterized by significant decrease in intestinal blood flow, oxygen uptake and redistribution of blood flow away from mucosal-submucosal the intestinal compartment. The results of these studies indicate that sensory C-fibers at rest, and when activated play a role in the control of intestinal blood flow, its distribution among vascular compartments of the intestinal wall and intestinal tissue oxygenation.