Myogenic mechanism for peristalsis in the cat esophagus

A myogenic control system (MCS) is a fundamental determinant of peristalsis in the stomach, small bowel, and colon. In the esophagus, attention has fo cused on neuronal control, the potential for a MCS receiving less attention . The myogenic properties of the cat esophagus were studied in vitro with a nd without nerves blocked by 1 mu M TTX. Muscle contraction was recorded, w hile electrical activity was monitored by suction electrodes. Spontaneous, nonperistaltic, electrical, and mechanical activity was seen in the longitu dinal muscle and persisted after TTX. Spontaneous circular muscle activity was minimal, and peristalsis was not observed without pharmacological activ ation. Direct electrical stimulation (ES) in the presence of bethanechol or tetraethylammonium chloride (TEA) produced slow-wave oscillations and spik e potentials accompanying smooth muscle contraction that progressed along t he esophagus. Increased concentrations of either drug in the presence of TT X produced slow waves and spike discharges, accompanied by peristalsis in 5 of 8 TEA- and 2 of 11 bethanechol-stimulated preparations without ES. Depo larization of the muscle by increasing KC concentration also produced slow waves but no peristalsis. We conclude that the MCS in the esophagus require s specific activation and is manifest by slow-wave oscillations of the memb rane potential, which appear to be necessary, but are not sufficient for my ogenic peristalsis. In vivo, additional control mechanisms are likely suppl ied by nerves.