Intramural mechanism of esophageal peristalsis: roles of cholinergic and noncholinergic nerves.

We examined the role of peripheral cholinergic and noncholinergic mechanisms in esophageal peristalsis. Intramural nerve elements in rings of circular muscle from six different levels of the opossum esophagus were stimulated transmurally so as to cause neurally mediated muscle contractions. Stimulus frequency was varied from 2 to 40 Hz. An increase in stimulus frequency caused an increase in latencies of contractions in rings from distal esophageal sites and a decrease in latencies in rings from proximal sites. This resulted in a marked slowing of the calculated peristaltic speed. Increasing stimulus frequency also caused an increase in duration and amplitude of contractions. These effects were reversed by atropine (0.1 microM), suggesting that higher stimulus frequencies recruited more cholinergic nerves. In the presence of atropine, increasing the stimulus frequency caused an increase in latencies of contraction at all sites, suggesting that increasing stimulation frequency applied to noncholinergic nerves causes an increase in latencies of contraction at all sites. The results of this study indicate that both noncholinergic and cholinergic nerves play a role in the peripheral mechanism of esophageal peristalsis. Cholinergic nerve stimulation reduces the latency and enhances the amplitude and duration of contractions seen with noncholinergic nerve stimulation alone. The influence of cholinergic innervation is most prominent proximally and decreases distally along the smooth muscle portion of the esophagus. This peripherally located gradient of cholinergic innervation plays an important role in determining the speed and amplitude of esophageal peristalsis.