Esophageal responses to transient and sustained esophageal distension

With the use of intraluminal manometry in alpha-chloralose-anesthetized opossums, distal esophageal and lower esophageal sphincter responses to prolonged midesophageal balloon distension were compared with those evoked by single transient distensions, vagal efferent stimulation, and swallowing. Balloon inflation caused sphincteric relaxation that recovered during small volume but persisted during large volume-prolonged distension. The esophageal body was either quiescent or exhibited nonperistaltic contractions during prolonged distension. Balloon deflation induced non-peristaltic esophageal and sphincteric contractions as well as further sphincter relaxation. Responses to prolonged large and small volume balloon distension resembled those evoked by high- and low-frequency vagal efferent stimulation, respectively. However, vagal-stimulated "on" contractions were not seen with balloon distension, and atropine did not modify excitatory responses occurring during or after prolonged distension. Although transient distension induced peristaltic esophageal contractions, the peristaltic velocity was faster than swallow-induced peristalsis. With transient distension, atropine prolonged the latency to contraction in the mid but not the distal smooth muscle segment and thus increased peristaltic velocity. These studies demonstrate that 1) esophageal distension evokes a wide spectrum of lower esophageal sphincter and esophageal body response, and 2) cholinergic neurons play a minimal role in distension-induced responses of the distal esophageal circular muscle below the distending balloon.