Electrical Activity of the Small Intestine With Special Reference to the Origin of Rhythmicity

Abstract

Unipolar recordings of small intestinal potentials were obtained from chronic dog preparations with exteriorized segments of bowel, from anesthetized dogs, cats and rabbits at laparotomy and from unanesthetized human subjects. Two dominant types of electrical activity were observed and correlated with function. The first type consisted of brief, nonpropagated, spike-like negative potentials which occurred only immediately preceding and during contraction and varied in frequency of occurrence proportionate to intensity of contraction. It is concluded that they represent the action potentials of contracting muscle fibers. The second type of electrical activity consisted of a recurring complex of slow potential changes, the configuration of which varied with the region of intestine and type of preparation. The complex was most stable and most clearly defined in transplanted segments of dog jejunum. The form of the complex was not altered by anesthetics or by sympathomimetic or parasympathomimetic drugs, and was the same during inactivity as during contractions. Initiation of contractions occurred only during the relatively positive phase of the slow complex. It is concluded that the slow complex is a cyclic alteration of the resting potential of the smooth muscle cells of the intestine which originates more or less synchronously in adjacent cells and is associated with a mechanism which renders the muscle alternately relatively excitable and absolutely refractory.