DOES THE PACEMAKER CURRENT GENERATE THE DIASTOLIC DEPOLARIZATION IN THE RABBIT SA NODE CELLS
DOES THE PACEMAKER CURRENT GENERATE THE DIASTOLIC DEPOLARIZATION IN THE RABBIT SA NODE CELLS
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DOI：
10.1007/bf00584356
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发表时间：
1983-01-01
影响因子：
4.5
通讯作者：
IRISAWA, H
中科院分区：
文献类型：
--
作者：
NOMA, A;MORAD, M;IRISAWA, H
采用2微电极技术，对自发跳动兔窦房结（SA结）的小制剂进行电压夹紧。研究了0.25 ~ 5 mM Cs+对自发起搏速率和随时间变化的内起搏电流ih的影响。在2 mM Cs+存在的情况下，自发起搏率仅略有下降，尽管在负至-60 mV的电位下ih被强烈抑制，但Cs+对钳形脉冲小于-50 mV时观察到的其他随时间变化的电流几乎没有影响。由于没有测量到Cs+对ih的电压依赖性（在-90和-20 mV之间），因此认为Cs+对舒张去极化速率的影响缺乏不太可能是由于Cs+对ih通道的电压依赖性效应造成的。肾上腺素在Cs+处理的窦房结细胞中产生明显的正变时作用。这种效应伴随着缓慢向内电流（isi）的显著增强，而Cs+阻断的ih电流没有变化。显然，ih在起搏器去极化的产生中起次要作用，表明isi在SA结细胞舒张期去极化的产生中起着更重要的作用。
Small preparations of spontaneously beating rabbit sino-atrial node (SA node) were voltage clamped with the 2-microelectrode technique. The effects of 0.25-5 mM Cs+ on the spontaneous pacing rate and the time-dependent inward pacemaker current, ih, were studied. In the presence of 2 mM Cs+, the spontaneous pacing rate decreased only slightly even though ih was strongly depressed at potentials negative to -60 mV Cs+ had little or no effect on other time-dependent currents observed with clamp pulses less negative than -50 mV. Since no voltage-dependence to the Cs+ effect on ih could be measured (between -90 and -20 mV), it was considered unlikely that the lack of Cs+ effect on the rate of diastolic depolarization results from a voltage-dependent effect of Cs+ on the ih channel. Adrenaline [epinephrine] produced a marked positive chronotropic effect in Cs+-treated SA node cells. This effect was accompanied by marked enhancement of the slow inward current (isi) with no change in the Cs+-blocked ih current. Apparently, ih plays a minor role in generation of pacemaker depolarization, and suggest a more prominent role of isi in the generation of diastolic depolarization in SA nodal cells.