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用固定频率起搏的离体豚鼠心乳头肌标本,研究了RTX对心肌膜电位及收缩力的影响。结果表明:RTX增加心肌Fc,降低RP和APA,缩短APD_(20)和APD_(50),其降低RP的作用与其增加Fc的作用相平行。RTX的全部效应均是时间和浓度依赖性的。在给RTx前和后加用TTX能分别减弱和逆转RTX的作用,并能迅速抵消RTX所诱发的自动节律活动。本实验结果提示:RTX能选择性地作用于心肌快Na~+通道,与TTX有拮抗作用,似可作为研究心肌离子转运的工具药之一。
The effects of RTX on myocardial membrane potential and contractile force were studied with isolated guinea pig papillary muscles pacing at a fixed frequency. The results showed that: RTX increased myocardial Fc, decreased RP and APA, shortened APD_ (20) and APD_ (50), and its effect of decreasing RP was in parallel with its effect of increasing Fc. The full effect of RTX is both time and concentration-dependent. The addition of TTX before and after RTx attenuated and reversed the effects of RTX, respectively, and quickly counteract the autonomic rhythm induced by RTX. Our results suggest that RTX can selectively act on fast Na ~ + channels in myocardium and antagonize TTX, which may be used as one of the tools to study myocardial ion transport.