Expression of dopamine receptors in human lower esophageal sphincter

Abstract

Dopamine (DA) is considered to be an important modulator of enteric function. Recent experiments have suggested that DA receptors are widely expressed in animal gastrointestinal tract. The aim of this study was to explore the expression of DA receptors (D(1) R, D(2) R, D(3) R, D(4) R, D(5) R) in sling fibers and clasp fibers from the human lower esophageal sphincter (LES). Muscle strips of sling and clasp fibers from the LES were obtained from patients undergoing esophago-gastrectomy, and circular muscle strips from the esophagus and stomach were used as controls. Reverse transcription-polymerase chain reaction and western blotting were used to determine the expression of the five subtypes of DA receptors. Messenger RNA and protein for three of five DA receptors were identified in the sling and clasp fibers of the LES. Expression was highest for D(1) R, then D(5) R and D(2) R in decreasing levels. D(3) R and D(4) R mRNA and protein were not identified in the muscle strips. D(1) R, D(2) R, D(5) R can be detected in the human LES, and probably contribute to LES function. D(3) R and D(4) R are not expressed, and probably do not contribute to LES function in humans.