Effect of thoracic vagotomy and vagal stimulation on esophageal function

The purpose of this study was to determine the effect of thoracic vagotomy and thoracic vagal stimulation upon esophageal peristalsis and lower esophageal sphincter (LES) function in the opossum. The thoracic portion of the vagus nerve was sectioned in the upper or lower thorax. Bilateral, but not unilateral, thoracic vagotomy above the level of the heart abolished peristalsis and LES relaxation in response to swallowing or cervical vagal electrical stimulation. Thoracic vagotomy at the level of the ventricle or below did not alter either peristalsis or LES relaxation during swallowing or cervical vagal stimulation. Secondary peristalsis and its associated LES relaxation was unaltered by thoracic vagotomy at any level. Electrical stimulation of the distal end of the upper thoracic vagus elicited both peristalsis and LES relaxation. Electrical stimulation of the distal end of the lower thoracic vagus elicited both peristalsis and LES relaxation. Electrical stimulation of the distal end of the lower thoracic vagus, as well as stimulation of the vagal branches to the terminal esophagus, gave only LES relaxation. These studies suggest that: a) the major extrinsic vagal innervation mediating primary peristalsis terminates in the upper portion of the esophagus, whereas the vagal innervation mediating LES relaxation responses are present throughout the length of the esophagus; and b) secondary peristalsis and its associated LES relaxation occurs independent of extrinsic vagal innervation.