Atropine inhibits gastric distension and pharyngeal receptor mediated lower oesophageal sphincter relaxation.

BACKGROUND Atropine decreases the frequency of transient lower oesophageal sphincter relaxation (TLOSR) through an unknown mechanism. Gastric distension and pharyngeal receptor excitation are two possible sources for the afferent stimulus responsible for TLOSR. AIMS To determine whether atropine affects gastric distension induced TLOSR and pharyngeal receptor mediated lower oesophageal sphincter (LOS) relaxation. METHODS Oesophageal manometry and pH recordings were performed in 10 healthy volunteers on two separate days in the postprandial setting, following either atropine (15 micrograms/kg intravenous bolus and 4 micrograms/kg/h as a maintenance dose) or placebo. Pharyngeal receptor mediated LOS relaxation was studied in nine subjects by rapid injection of minute amounts 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 eight 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 LOS relaxation. Atropine decreased the frequency and amplitude of pharyngeal receptor mediated LOS relaxation at bolus volumes of 0.05, 0.1, and 0.2 ml. Gastric distension resulted in intermittent episodes of TLOSR. The frequency of gastric distension induced TLOSR was significantly decreased by atropine. CONCLUSION (1) Atropine reduces the frequency of spontaneous reflux and TLOSR in normal subjects; and (2) gastric distension induced TLOSR and pharyngeal receptor mediated LOS relaxation is inhibited by atropine.