Effect of atropine on the frequency of reflux and transient lower esophageal sphincter relaxation in normal subjects.

BACKGROUND & AIMS: Low basal lower esophageal sphincter (LES) pressure is believed to be an important mechanism of reflux. The effects of atropine on the frequency and mechanisms of gastroesophageal reflux under the experimental conditions of a low basal LES pressure in 13 normal subjects were studied.
METHODS: LES pressure, esophageal pressures, esophageal pH, and crural diaphragm electromyogram were recorded simultaneously in the postprandial period for 30 minutes before and two 30-minute periods after the injection of atropine.
RESULTS: Atropine reduced the basal LES pressure from 16.4 +/- 3 to 8.7 +/- 2 mm Hg. The frequencies of reflux in the control and two postatropine periods were 3.5 +/- 0.5, 0.4 +/- 0.2, and 0.8 +/- 0.3, respectively (P < 0.05). The frequencies of transient LES relaxations decreased from 3.5 +/- 0.5 in the control to 0.4 +/- 0.2 and 1.5 +/- 0.4 in the two postatropine periods (P < 0.05). Transient LES relaxation and associated inhibition of the crural diaphragm was the major mechanism of reflux under conditions of low LES pressure induced by atropine.
CONCLUSIONS: Atropine-induced low LES pressure does not predispose to reflux in normal healthy subjects. Atropine reduces the frequency of reflux by its inhibitory effect on the frequency of transient LES relaxation.