Vagal esophageal receptors in anesthetized dogs: mechanical and chemical responsiveness

This study was performed to evaluate the characteristics of esophageal receptors in anesthetized and artificially ventilated dogs. The electrical activity of the esophageal afferents was recorded from the peripheral cut end of the cervical vagus nerve. A cuffed catheter was inserted into the esophagus at the level of the third tracheal ring and was used to establish the esophageal location of the endings. Most of the receptors were localized in the intrathoracic portion of the esophagus. The majority of the receptors studied (36 of 43) showed a slow adaptation to a maintained stretch of the esophageal wall. Vagal cooling blocked receptor activity at temperatures ranging from 3.5 to 25 degrees C. Twenty-eight of 43 receptors, including 4 rapidly adapting endings (RAR), were challenged with saline, HCl + pepsin (HCl-P; pH 1) and distilled water (8 ml, 37 degrees C). HCl-P solutions specifically stimulated only three receptors; saline or water did not. Five slowly adapting receptors and two RARs were also challenged with topically applied capsaicin; only one RAR was stimulated. To ascertain a possible effect of smooth muscle contraction, 17 receptors were tested with intravenous injections of ACh and/or asphyxia; only 4 were stimulated. These characteristics do not support an important reflexogenic role of the esophagus in response to chemical stimuli.