Caffeine and Ryanodine May Act on the Plasma Membrane of the Circular Muscle at the Flexure Region in the Guinea-Pig Colon

概要

論文の詳細を見る
The actions of caffeine and ryanodine on the spontaneous rhythmic activities in the guinia-pig colon were studied by mechanical tension recording. Caffeine reduced the amplitude of the spontaneous rhythmic activity at low concentration (0.3mM-1mM). At high concentration (3-10mM), it induced a phasic transient contraction. The spontaneous rhythmic activity and a phasic contraction induced by caffeine, were blocked by verapamil (3μM) or by removal of external Ca^2+. Ryanodine affected neither resting tension nor frequency of spontaneous activity at 1μM. However in the circular muscle strips pretreated with ryanodine, a sustained contraction was initiated after the removal of caffeine (10mM). Continuous Ca^2+ influx was necessary for spontaneous rhythmic activities and a phasic transient contraction, because it was abolished completely by the removal of external Ca^2+. Verapamil (3μM), a voltage gated L-type Ca^2+ channels blocker, inhibited the spontaneous thythmic activities and also inhibited phasic transit contraction followed by a sustained contraction induced by 10mM caffeine. Our results suggest that caffeine may produce a sustained contraction by activating verapamil sensitive Ca^2+ channel. In the muscle pretreated with both caffeine and ryanodine, continuous Ca^2+ influx may occur also through verapamil sensitive pathway.
日本平滑筋学会の論文