Relation between small intestinal motility and circulation.

Effects of muscular activity on local blood flow have been delineated in other muscular organs but are part of a complex relationship in the small intestine. Some of our inability to provide a clear picture of the circulatory events surrounding intestinal motility relates to the variety of imprecise techniques that have been used to explore the relationship. Distension of the gut impedes blood flow through the intestinal wall, especially in the mucosa. Stimulation of motility evokes more variable responses in the intestinal circulation, including increases in blood flow; however, the circulatory response reflects mostly the nature of the intervention used to activate motility. Many motor stimuli in the gut have intrinsic vasoactive properties. Spontaneous motor events seem to have only small effects on total blood flow to the small intestine. Reduction in blood flow to the gut evokes initial increases in motility followed by inhibition of motor activity. Products of metabolism in the intestine influence both motor and vascular reactivity. More sensitive methods need to be developed to separate the types of intestinal motor activity, to localize mechanical events in specific sites in the wall of the gut, to better record electrical correlates of motility, and to measure local tissue blood flow. These technical developments will permit delineation of the linkage between motor and vascular events and should identify the regulatory factors.