迷走神经对家兔在体心脏心室肌细胞跨膜电位的影响

本研究观察了电刺激迷走神经对家兔在体心脏心室肌细胞跨膜电位的作用及钾通道阻滞剂氯化四乙基铵对这一作用的影响。结果表明,在自然心率条件下,迷走神经刺激可使静息电位(RP)、动作电位振幅(APA)和0相最大上升速率(dv/dt)_(max)增加,动作电位时程(APD)缩短。冠脉注射氯化四乙基铵使心室肌细胞复极过程明显延长,迷走神经刺激不再引起 RP、APA 增大,动作电位时程不再缩短,(dv/dt)_(max)反而减小。这些结果提示,迷走神经刺激对正常心室肌细胞跨膜电位的影响可能是通过外向 K~ 流增加引起的。

EFFECTS OF VAGAL STIMULATION ON TRANSMEMBRANE POTENTIALS OF IN SITU RABBIT'S CARDIAC VENTRICULAR FIBERS

Transmembrane potentials of rabbit's cardiac ventricular fibers were recordedwith floating microelectrode technique in situ.Vagal stimulation caused an in-crease in resting potential(RP),action potential amplitude(APA)and maximumupstroke velocity of phase 0(dv/dt)_(max) and shortening of action potential duration(APD).These effects were unrelated to heart rate.However,the shortening effectof vagal stimulation on APD was masked by slowing of heart rate.Intracoronaryarterial injection of K channel blocker tetraethylammonium chloride greatly retaredthe rate repolarization of action potential,abolished the effect of vagal stimulationto increase RP and APA,APD can no longer be shorted,while(dv/dt)_(max) wasdecreased.These results suggested that the influence of vagal stimulation on mem-brane potential of cardiac ventricular fiber might be due to an increase of outwardpotassium current.