Electrical control of canine jejunal propulsion

We wondered whether the direction of propagation of intestinal pacesetter potentials determines the direction of movement of intestinal content. In six dogs, electrodes for pacing were implanted near each end of an 80-cm isolated jejunal loop, and a cannula was positioned at the middle of the loop for intraluminal insertion of solids and/or liquids. After recovery and during fasting, 50 nylon spheres (2 mm diam) always emptied from the distal stoma regardless of the direction of pacing. In contrast, 150 mM NaCl, given alone at 2.8 ml/min or with spheres, emptied from the distal stoma during forward pacing and from the proximal stoma during backward pacing. Spheres given with the liquid emptied from the distal stoma during forward pacing, but during backward pacing, the site of emptying varied among dogs. Neither pacing nor spheres altered jejunal interdigestive myoelectric cycles, but the perfusate abolished the cycles and resulted in a noncyclic pattern of jejunal action potentials. We concluded that the direction of pacesetter potential propagation determined the direction of liquid transit. Direction of solid transit depended, in part, on other mechanisms.