Nervous Control of Distension-Induced Relaxation of the Porcine Lower Oesophageal Sphincter

The mechanisms involved in the relaxation of the lower oesophageal sphincter induced by distension of the oesophagus and different parts of the stomach, were studied in an anaesthetized porcine model. A computer technique was developed allowing on-line digitizing of lower oesophageal sphincter (sleeve device) and intragastric pressures. Basal sphincter tone was slightly reduced by truncal vagotomy, an effect which seemed to be reversed by sectioning of the vagosympathetic trunks in the neck. Balloon distension of the body of the oesophagus, relaxed the sphincter irrespective of the denervation procedures carried out. Distension of the whole stomach with increasing amounts of air induced a dose-dependent relaxatory lower oesophageal sphincter response, which was also closely associated with the subsequent increases in intragastric pressure. Denervation procedures did not alter this dose-response relationship. The importance of intramural mechanisms was illustrated by the abolition of distension-induced effects in most animals studied after transection of the gastro-oesophageal junction distal to the sphincter. Balloon distension of the antrum elicited a smaller but significant sphincter relaxation, but the mechanisms behind this response seemed to be more complex than after insufflation of air.