Introduction: A sub-threshold pharyngeal stimulus induces lower esophageal sphincter (LES) relaxation and inhibits progression of ongoing peristaltic contraction in the esophagus. Recent studies show that longitudinal muscle contraction of the esophagus may play a role in LES relaxation. Aim: Our goal was to determine if a sub-threshold pharyngeal stimulus induces contraction of the longitudinal muscle of the esophagus and to determine the nature of this contraction. Methods: Studies were conducted in 16 healthy subjects. High resolution manometry (HRM) recorded pressures and high frequency intraluminal ultrasound (HFIUS) images recorded longitudinal muscle contraction at various locations in the esophagus. Sub-threshold pharyngeal stimulation was induced by injection of minute amounts of water in the pharynx. Results: A sub-threshold pharyngeal stimulus induced strong contraction and caudal descent of the upper esophageal sphincter (UES) along with relaxation of the LES. HFIUS identified longitudinal muscle contraction of the proximal (3-5 cm below the UES) but not the distal esophagus. Pharyngeal stimulus, following a dry swallow, blocked the progression of dry swallow induced peristalsis; this was also associated with UES contraction and descent along with the contraction of longitudinal muscle of the proximal esophagus. Conclusions: We identify a unique pattern of longitudinal muscle contraction of the proximal esophagus in response to sub-threshold pharyngeal stimulus, which we propose may be responsible for relaxation of the distal esophagus and LES through the stretch sensitive activation of myenteric inhibitory motor neurons.
- Upper Esophageal Sphincter
- Longitudinal Muscle of Esophagus
- Stretch Sensitive LES relaxation
- Mechanosensitive Motor Neurons
- Copyright © 2011, American Journal of Physiology- Gastrointestinal and Liver Physiology