Intrinsic nervous control of migrating myoelectric complexes

Abstract

The role of intrinsic nerves in the control of migrating myoelectric complexes (MMCs) was studied in seven conscious dogs, each implanted with a set of eight bipolar Trimel wire electrodes. Local areas, 3-5 cm long, were perfused close intra-arterially via an exteriorized heparinized Silastic cannula. Experiments consisted of giving bolus injections of atropine (20-50 micrograms), hexamethonium (20 mg), and tetrodotoxin (TTX; 3-30 micrograms) via the catheter at varying periods of time with respect to the arrival of phase III at the perfused site. Atropine and hexamethonium, given close intra-arterially immediately before the arrival of phase II at the perfused site, blocked its further propagation. Tetrodotoxin given locally also blocked the propagation of phage III, as above. After the block, TTX initiated a new phase III activity at, or distal to, the perfused site in 10 out of 14 perfusions. The new phase III activity propagated distally. This study shows that the mechanisms for the initiation and propagation of MMCs are built into the enteric plexus. Once an MMC is initiated, its propagation is achieved by proximal-to-distal excitation through the intrinsic cholinergic network of neurons. This study explains the lack of any significant changes in the propagation parameters of MMCs after vagotomy or celiac and superior mesenteric ganglionectomy.