Noma A, Kotake H, Kokubun S, Irisawa H
Jpn J Physiol. 1981;31(4):491-500. doi: 10.2170/jjphysiol.31.491.
The slow inward current (is) in the rabbit sinoatrial node cell was studied by the conventional two-microelectrode voltage clamp technique. When is was measured as the difference between two records obtained before and after blocking is with D 600, the fully activated current (is)-voltage relation was non-linear; the conductance decreased in the negative potential range resulting in an almost constant amplitude of is negative to -10 mV. The degree of steady-state activation was about 1 at -5mV and 0 at -65mV. The recovery time course of is during repolarization was measured by varying the interval between two sequential depolorizing pulses with various holding potentials. The time constant of the exponential recovery time course was about 120 msec at -40 mV and decreased to about 40 msec at -70 mV. The steady-state conductance of is, calculated from the activation and inactivation curves, produced a large hump in the steady-state current voltage relation between -60 and -20 mV, which was not observed in the experiment. When the above kinetics were incorporated, the S-A node model failed to discharge the spontaneous activity. The activation and inactivation curves which can simulate the experimental I-V curve and the action potential were proposed.
采用传统的双微电极电压钳技术研究了兔窦房结细胞的缓慢内向电流（is）。当通过用D 600阻断is前后获得的两个记录之间的差值来测量is时，完全激活的电流（is）-电压关系是非线性的；在负电位范围内电导降低，导致is在负于-10 mV时幅度几乎恒定。稳态激活程度在-5 mV时约为1，在-65 mV时为0。通过改变两个连续去极化脉冲之间的间隔以及不同的钳制电位来测量复极化期间is的恢复时间进程。指数恢复时间进程的时间常数在-40 mV时约为120毫秒，在-70 mV时降至约40毫秒。根据激活和失活曲线计算的is的稳态电导在-60至-20 mV之间的稳态电流-电压关系中产生了一个大的峰，这在实验中未观察到。当纳入上述动力学时，窦房结模型无法产生自发活动。提出了能够模拟实验I-V曲线和动作电位的激活和失活曲线。
