The effect of atropine on the gastroesophageal sphincter

Abstract

Pressure characteristics of the stomach, gastroesophageal sphincter, and esophagus were studied in 14 normal subjects to assess the effect of atropine, under resting conditions and during abdominal compression. The investigations were carried out in two parts. In part I manometric recordings from each subject were made on two separate days. On the control day, two separate injections of saline were given and pressures were recorded with and without abdominal compression following each injection. On the test day, the procedure was identical except that atropine (0.015 mg/kg) was substituted for the second injection of saline. In part II of the investigation, pressures from each subject were recorded on one day only. An initial injection of saline was given, followed by pressure recordings. Atropine was then given at a dosage of 0.025 mg/kg and the recordings were repeated. The pressure characteristics of the stomach, sphincter (maximum), and esophagus did not significantly vary at different times on the same day, or subsequent days. The higher dosage of atropine caused a significant reduction in the mean maximum pressure in the sphincter both under resting conditions and during abdominal compression but did not affect pressures in the stomach or esophagus. The drug had a more pronounced effect on the response of the sphincter to abdominal compression than on the resting pressure of the sphincter. From these observations it is concluded that a cholinergic mechanism is partly responsible for the pressure maintained in the gastroesophageal sphincter under resting conditions. This vagal influence is also an important component involved in maintaining the functional integrity of the gastroesophageal sphincter during abdominal compression.