A study of the effect of the rate of stimulation on the transient outward current in sheep cardiac Purkinje fibres.
A study of the effect of the rate of stimulation on the transient outward current in sheep cardiac Purkinje fibres.
复制标题
刺激速率对绵羊心脏浦肯野纤维瞬态外向电流影响的研究。
DOI：
10.1113/jphysiol.1981.sp013888
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发表时间：
1981
期刊：
影响因子：
--
通讯作者：
M. Boyett
中科院分区：
文献类型：
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作者：
M. Boyett
1.使用双微电极电压钳技术记录了绵羊浦肯野纤维的瞬时外向电流Ito。2. Ito具有很强的速率依赖性：在一系列动作电位之后的测试电压钳脉冲期间激活的Ito的幅度在较高的刺激速率下较小。3.在频率增加或减少之后，在第一个响应中Ito会发生突然变化，然后在接下来的几百个响应中发生缓慢变化。4.当一种制剂在重复活动后休息时，伊藤在两秒钟内恢复：在最初的10秒内有一个快速的、近似指数的恢复阶段，这可能是由于再激活;随后是一个持续数百秒的缓慢恢复阶段。5.在不同的速率下获得了显示伊藤再激活的时间过程的曲线。在高速率下，曲线接近较小的Ito值，并且电流的稳态控制值出现在曲线的肩部，即在重新激活完成之前。6.有人建议，减少伊藤在高利率是由于两个因素：不完全的重新激活，占伊藤的快速变化和第二个未知因素，占电流的变化较慢。7. Ito的电流-电压关系的检查表明，在高速率下Ito的降低主要是由于电导的降低，而不是由于反转电位的降低。8.用锶代替浴液中的钙并不能消除绵羊浦肯野纤维中的Ito，这表明该电流不同于Siegelbaum和Tsien（1980）描述的小牛浦肯野纤维中的瞬时外向电流。
1. The transient outward current, Ito, of sheep Purkinje fibres has been recorded using the two micro‐electrode voltage clamp technique. 2. Ito is strongly rate‐dependent: the magnitude of Ito activated during a test voltage clamp pulse after a train of action potentials is less at higher rates of stimulation. 3. After an increase or decrease in rate there is an abrupt change in Ito in the first response followed by slower changes over the next several hundred responses. 4. When a preparation is rested after repetitive activity Ito recovers in two phages: there is an initial rapid, approximately exponential phase of recovery in the first 10 s which is probably due to reactivation; this is followed by a slower phase of recovery lasting several hundred seconds. 5. Curves showing the time course of reactivation of Ito have been obtained at different rates. At high rates the curves approach smaller values of Ito and the steady‐state control values of the current occur on the shoulder of the curves, i.e. before reactivation is complete. 6. It is proposed that the reduction of Ito at high rates is due to two factors: incomplete reactivation which accounts for the rapid changes of Ito and a second unknown factor which accounts for the slower changes in the current. 7. Inspection of current‐voltage relationship for Ito suggests that the reduction of Ito at high rates is mainly due to a decrease of conductance rather than to a reduction of the reversal potential. 8. Replacement of the calcium in the bathing solution by strontium does not abolish Ito in sheep Purkinje fibres, suggesting that the current is distinct from the transient outward current in calf Purkinje fibres described by Siegelbaum & Tsien (1980).