Depolarizing Mechanisms of Acetylcholine in Gastric Smooth Muscle

Jun, Jae Yeoul; Yeum, Cheol Ho; Moon, Sung Ho; Oh, Hyeong Kyun; Park, Yoo Whan; Lee, Sang Jin; Yun, Pyung Jin

Abstract

BACKGROUND AND AIMS: Acetylcholine which is a major excitatory neurotransmitter, depolarizes gastric smooth muscle cells. The aim of this study was to investigate the ionic mechanisms of acetylcholine-induced depolarization in antral myocytes of guinea-pig.
METHODS
Gastric myocytes were isolated from the antral circular layer of guinea-pig using a collagenase. Then, we recorded membrane currents using the whole-cell patch clamp method.
RESULTS
Acetylcholine suppressed Ca2+- dependent K+ currents, whereas delayed rectifier K+ currents and voltage dependent Ca2+ currents were not changed. Under voltage clamp at -50 mV, acetylcholine activated inward currents. It was characterized by voltage-dependent and Ca2+-dependent cationic current. In the high concentration of extracellular K+ (90 mM), lemakalim produced inward currents, which could be blocked by glibenclamide, a specific blocker of ATP-sensitive K+ channel. Acetylcholine suppressed these glibenclamide-sensitive K+ currents.
CONCLUSIONS
The results of this study suggested that the depolarizing mechanism of acetylcholine might be caused from the combined effects of the suppression of Ca2+-dependent K+ currents, the activation of non-specific cationic current and the suppression of glibenclamide-sensitive K+ currents.