常咯啉对豚鼠心室乳头肌的频率及使用依赖性等电生理作用

运用标准玻璃微电极、微机实时分析技术及特异性离子阻断剂研究常咯啉(CRL)对豚鼠心室乳头肌的作用。常咯啉对动作电位的(?)_(max)呈现浓度依赖、频率依赖和使用依赖性阻断作用。用钾离子阻断剂CsCl 15μmol/L后,常咯啉不再缩短APD,用高钾使细胞部分除极后,常咯啉使动作电位的(?)_(max)下降,APD延长,ERP相对延长。部分除极标本用钙离子阻断剂维拉帕米3μg/ml后,常咯啉不再延长APD。可见,常咯啉不仅阻钠内流,且可能有促钾外流和促钙内流的作用。

The electrophysiological effects of changrolin on frequency and use-dependence in guinea pig papillary muscles

Some researches about changrolin (CRL) have been reported previously. Here, we studied the effects of CRL in guinea pig papillary muscles by means of the standard microelectrode techniques in vitro in other aspects for further analysing the mechanism of the effect of CRL.CRL caused a dose-dependent decrease of Vmax of the action potential without affecting the resting potential. CRL reduced Vmax in a frequency-dependent way in the range of 0.25-2 Hz. The onset of use-dependent Vmax reduction at 3.3 Hz followed a monoexponential function with a slow rate constant of 0.0305 ± 0.0013 AP-1 (CRL is therefore classified as a "slow" I class antiarrhythmic agent). In the presence of 15μmol/L CsCl after the blockage of potassiumconductance, CRL did not significantly reduce APD. When a papillary muscle was exposed to 15.6 mmol / L K.Cl, CRL significantly prolonged APD, which was not modified by further addition of 3 μg / ml verapamil (known as calcium blocker). The results suggested CRL depress sodium conductance as well as promote calcium and potassium conductance. The greater inhibition of Vmax and its frequency- and use-dependence through an increment of tonic block may play a major role in the prevent of ventricular arrhythmias by CRL.