BACKGROUND AND AIMS Distension of the proximal stomach is a major stimulus for triggering transient lower oesophageal sphincter (LOS) relaxations. We have shown recently that atropine inhibits triggering of transient LOS relaxations in both normal subjects and patients with gastro-oesophageal reflux disease. Atropine could potentially act centrally by inhibiting the central integrating mechanism in the brain stem, or act peripherally by altering the response of the stomach to distension. The aim of this study was to investigate the effect of atropine on fasting gastric compliance and postprandial gastric tone using an electronic barostat.

RESULTS In the fasting period, atropine significantly reduced minimum distending pressure (5.5 (0.4) v 4.4 (0.4) mm Hg; p<0.005) and increased proximal gastric compliance (81.3 (5.3)v 102.1 (8.7) ml/ mm Hg; p<0.05). In response to a meal, maximal gastric relaxation was similar on both study days. However, during atropine infusion, there was no recovery of proximal gastric tone in the two hour postprandial observation period. Postprandial fullness scores were higher during atropine infusion and correlated with changes in intrabag volume. Atropine significantly reduced the rate of postprandial transient LOS relaxations: first hour, 7.0 (5.3–10.0) v 3.0 (1.0–4.0) (p<0.02); second hour, 5.0 (3.3–5.8) per hour v 1.0 (0–3.0) per hour (p<0.05).

CONCLUSIONS In humans, fasting and postprandial proximal gastric motor function is under cholinergic control. Atropine induced inhibition of transient LOS relaxations is unlikely to be caused by its effect on the proximal stomach, but rather by a central action on the integrating mechanisms in the brain stem.