离子通道阻断剂对家兔左心室流出道的电生理效应

目的:研究左心室流出道自律性及其电生理特性。方法:本实验利用常规的玻璃微电极细胞内记录技术,观察了常规离子通道阻断剂对离体家兔左心室流出道慢反应自律细胞的电生理特性的影响,重点探讨了该部位自律细胞的0期、4期去极离子流。结果:1用1.2mmol/L河豚毒(TTX)使动作电位幅值(APA)、0期最大除极速率(Vmax)与给药前相比明显减小(P<0.05),舒张期除极速率(VDD)和自发放电频率(RPF)均明显减慢(P<0.01);2用0.5μmol/L维拉帕米(VER)灌流后APA、Vmax、最大舒张电位(MDP)绝对值、VDD、RPF均明显下降,复极90%时间(APD90)延长(P<0.05);3用120μmol/L氯化镍(NiCl2)灌流,VDD明显下降,APA、Vmax、RPF也显著降低;4给予2mmol/L4-氨基吡啶(4-AP)后VDD明显增快,MDP绝对值、APA、Vmax显著下降,APD90明显延长(P<0.05);5给予1.5mmol/L氯化铯(CsCl)后VDD及RPF均明显变慢(P<0.05)。结论:1Ca2+流为兔左心室流出道自律细胞0期去极主要离子流,并有少量Na+内流参与;24期自动除极以K+外流衰减为主,另外,ICa-T、ICa-L及If在起搏电流中也起一定作用。

Electrophysiological effects of some ionic channel blockers on the left ventricular outflow tract of rabbit

Objective:To clarify automaticity and the electrophysiological characteristics of the pacemaker cells in the left ventricular outflow tract. Methods: By using conventional intracellular microelectrode technique to record spontaneous slow action potentials, some ionic channel blockers were used to observe their electrophysiological effectson pacemaker cells in the rabbit, especially on the ionic movement during phase 0 and phase 4. Results: ①1.2mmol/L tetrodotoxin(TTX) significantly decreased APA and Vmax(P<0.05), while VDD and RPF were significantly slowed down as compared with control(P<0.01); ②Perfusion with 0.5μmol/L Verapamil (VER) resulted in a significant reduction of the amplitude of action potential (APA), maximal rate of depolarization (Vmax), absolute value of the maximal diastolic potential (MDP), velocity of diastolic depolarization (VDD) and rate of pacemaker firing(RPF), and a prolongation of the 90% duration of action potential (APD 90)(P<0.05); ③Perfusion with 120μmol/L nickel chloride (NiCl_2) resulted in a decrease in VDD(P<0.01), APA, Vmax, RPF fell notably, and the APD_ 90 prolonged (P<0.05); ④2mmol/L 4-aminopyridine (4-AP) led to a increase in VDD (P<0.01). At the same time the absolute value of MDP, APA, Vmax decreased significantly, and APD_ 90 prolonged notably (P<0.05); ⑤1.5mmol/L cesium chloride (CsCl) led to a decrease in VDD and RPF (P<0.05). Conclusion: ①Generation of 0 phase of depolarization of slow-response activity in the left ventricular tract is contributed mainly by Na+ current in addition to Ca 2+; ②Attenuation of K+ current is responsible for the phase 4 spontaneous depolarization. In addition, it seems that I_ Ca-T,I_ Ca-L and I_f play some role in the pacemaker currents.