ATROPINE INHIBITS GASTRIC DISTENSION AND PHARYNGEAL RECEPTOR-MEDIATEDLOWER ESOPHAGEAL SPHINCTER RELAXATION

Background-Atropine decreases the frequency of transient lower oesopha geal sphincter relaxation (TLOSR) through an unknown mechanism. Gastri c distension and pharyngeal receptor excitation are two possible sourc es for the afferent stimulus responsible for TLOSR. Aims-To determine whether atropine affects gastric distension induced TLOSR and pharynge al receptor mediated lower oesophageal sphincter (LOS) relaxation. Met hods-Oesophageal manometry and pH recordings were performed in 10 heal thy volunteers on two separate days in the postprandial setting, follo wing either atropine (15 mu g/kg intravenous bolus and 4 mu g/kg/h as a maintenance dose) or placebo. Pharyngeal receptor mediated LOS relax ation was studied in nine subjects by rapid injection of minute amount s of water (0.05, 0.1, 0.2, 0.3, and 0.4 ml) in the pharynx before and after atropine. Gastric distension mediated TLOSR was studied in eigh t subjects by insufflating the stomach with 300, 600 and 900 ml of CO2 before and after atropine. Results-Atropine reduced the frequency of spontaneous gastro-oesophageal reflux and TLOSR compared with placebo (p<0.05). Pharyngeal stimulation resulted in bolus volume dependent LO S relaxation. Atropine decreased the frequency and amplitude of pharyn geal receptor mediated LOS relaxation at bolus volumes of 0.05, 0.1, a nd 0.2 mi. Gastric distension resulted in intermittent episodes of TLO SR. The frequency of gastric distension induced TLOSR was significantl y decreased by atropine. Conclusion-(1) Atropine reduces the frequency of spontaneous reflux and TLOSR in normal subjects; and (2) gastric d istension induced TLOSR and pharyngeal receptor mediated LOS relaxatio n is inhibited by atropine.