Effects of dl-tetrahydropalmatine on the slow response action potentials in rabbit sinoatrial node and guinea pig papillary muscle
ZHAO Dong-ke, ZHAO Geng-sheng, QIU Pei-lun, LI Xiao-guang, ZHAO Yong-qiangDept of Pharmacology, Research Laboratory of Electronic Engineering, Xian Medical University, Xian 710033
dl-Tetrahydropalmatine(THP) is an alkaloid isolated from Corydalis turtschaninovii Bess. f. Yanhusuo Y. H. Chow et C. C. Hso. It was reported that THP had antiarrhythmic and calcium-antagonistic effects. In our laboratory effects of THP on the spontaneous electrical activity in rabbit sinoatrial node and the slow response action potentials induced by K+ (25 mM) and tetrodotoxin (TTX) (2μM) inguinea pig papillary muscle were observed by using glass microelectrode and in vitro perfusion technique.When the sinoatrial node cells were exposed to 30μM, 56 μM or 100 μM THP, their action potential amplitude (APA), slope of phase 0 (SP4), slope of phase 4 (SP4) and heart rate (HR) were decreased . THP prolonged the action potential duration to 90% repolarization (APD90)at the concentra tion of 30μM, but shortened APD90 at the concentration of 100 μM. All changes described above were significant. (p0.05 or p0.01).In guinea pig papillary muscles, THP 100μM or 300 μM decreased maximal depolarization rate of phase 0 (Vmax) and APA and shortened APD50 and APD90 in the slow response action potentials induced by K+and TTX. 30 μM THP decreased Vmax of both K+ and TTX action potentials and prolonged APD90 of the action potential induced by K+ without any significant effects on other para-meters of slow response action potentials. The experimental results showed that THP inhibited the spontaneous electrical activity of rabbit sinoatrial node and the slow response action potentials induced by K+and TTX. It is suggested that THP may be a calcium channel blocker.
【Fund】： 国家自然科学基金NO 3860855