Vagal esophageal receptors in anesthetized dogs: mechanical and chemical responsiveness

This study was performed to evaluate the characteristics of esophageal rece ptors in anesthetized and artificially ventilated dogs. The electrical acti vity of the esophageal afferents was recorded from the peripheral cut end o f the cervical vagus nerve. A cuffed catheter was inserted into the esophag us at the level of the third tracheal ring and was used to establish the es ophageal location of the endings. Most of the receptors were localized in t he intrathoracic portion of the esophagus. The majority of the receptors st udied (36 of 43) showed a slow adaptation to a maintained stretch of the es ophageal wall. Vagal cooling blocked receptor activity at temperatures rang ing from 3.5 to 25 degrees C. Twenty-eight of 43 receptors, including 4 rap idly adapting endings (RAR), were challenged with saline, HCl + pepsin (HCl -P; pH 1) and distilled water (8 mi, 37 degrees C). HCl-P solutions specifi cally stimulated only three receptors; saline or water did not. Five slowly adapting receptors and two RARs were also challenged with topically applie d capsaicin; only one RAR was stimulated. To ascertain a possible effect of smooth muscle contraction, 17 receptors were tested with intravenous injec tions 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.