Mechanisms of enhanced canine enteric absorption with intestinal pacing

Electrical pacing enhances absorption from the canine small bowel, but the mechanism of this effect is unknown. To explore the mechanism, conscious dogs with two Vella loops, a proximal jejunal and a distal ileal, each 50 cm long, were studied. Pacing the jejunal loop with 15-18 pulses/min entrained the pacesetter potentials of the jejunal loop and increased water, sodium, and glucose absorption from the jejunal loop. Jejunal pacing also increased water absorption from the unpaced, ileal loop. Conversely, ileal pacing did not entrain the ileal loop or enhance absorption from the ileal loop. However, it did enhance water absorption in the unpaced jejunal loop. After alpha-blockade with phentolamine or celiac and superior mesenteric ganglionectomy, jejunal pacing did not increase jejunal or ileal absorption. In contrast, after beta-blockade with propranolol, pacing still enhanced jejunal absorption in three out of four dogs. Vagotomy alone enhanced jejunal but not ileal absorption, but the enhancement was not further increased by pacing. In conclusion, electrical pacing of the small bowel elicited a local and distant increase in net water absorption; the effect was mediated in part by an alpha-adrenergic mechanism.