Effect of atropine on proximal gastric motor and sensory function in normal subjects

Background and aims-Distension of the proximal stomach is a major stimulus far triggering transient lower oesophageal sphincter (LOS) relaxations. We have shown recently that atropine inhibits triggering of transient LOS rela xations in both normal subjects and patients with gastro-oesophageal reflux disease. Atropine could potentially act centrally by inhibiting the centra l 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 inv estigate the effect of atropine on fasting gastric compliance and postprand ial gastric tone using an electronic barostat. Methods-Fasting and postprandial proximal gastric motor and sensory functio ns were assessed in 10 normal healthy volunteers. Oesophageal manometry and pH were simultaneously measured. On separate days, atropine (15 mu g/kg bo lus, 4 mu g/kg/h intravenous infusion) or saline was given and maintained f or the duration of the recording period. Results-In the fasting period, atropine significantly reduced minimum diste nding pressure (5.5 (0.4) v 4.4 (0.4) mm Hg; p<0.005) and increased proxima l gastric compliance (81.3 (5.3) v 102.1 (8.7) ml/ mm Hg; p<0.05). fn respo nse to a meal, maximal gastric relaxation was similar on both study days. H owever, during atropine infusion, there was no recovery of proximal gastric tone in the two hour postprandial observation period. Postprandial fullnes s scores were higher during atropine infusion and correlated with changes i n 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 func tion is under cholinergic control. Atropine induced inhibition of transient LOS relaxations is unlikely to be caused by its effect on the proximal sto mach, but rather by a central action on the integrating mechanisms in the b rain stem.