These studies were performed in the duodenum of dogs to elucidate the following problems, 1) the role of the extrinsic nerves on the electrical activities, 2) the effects of pancreozymin, gastrin and secretin, 3) the existence of pacemaker, 4) the manner of slow wave conduction, and 5) the effect of hypoxia.
The electrical activities of the duodenum are scarcely influenced by vagal nerve and mesenteric plexus but controled by a certain pacemaker locating at the upper duodenum cranial to the papilla of Vater.
Intravenous administration of pancreozymin provokes the vigorous contraction of the intestine, which is recognized at the same time as spike potentials electromyographically. Gastrin lowers the slow wave potential or abolishes it. No change is observed in case of secretin.
It may be suggested that in the duodenum there is a mechanism similar to the impulse conducting system in the heart, which was postulated by Keith in 1915. When the slow wave potential is low or near zero level, the contraction of the intestine does not occur. Therefore the fact shows that the slow wave potential for the contraction of the intestine must be higher than a certain level. The low potential of slow waves induced by rapid withdrawal of blood or by clamping the vessels nourishing a segment of the intestine indicates the invalidity of the longitudinal smooth muscle cells of the intestine caused by hypoxia.
