Ito S, Surawicz B
Am J Physiol. 1981 Aug;241(2):H139-44. doi: 10.1152/ajpheart.1981.241.2.H139.
Intracellular loading with 20 mM tetraethylammonium chloride (TEA) diffusing through the cut end of the preparations prolonged action potential duration (APD) in dog Purkinje fibers without changing maximum diastolic potential, overshoot, and dV/dtmax. The APD was prolonged at all rates of stimulation, but, contrary to the normal rules, APD increased more after longer than after shorter interstimulus intervals. TEA increased the number of beats required to achieve the new steady-state APD after an abrupt change in the rate of stimulation. The effect of varying extracellular potassium concentration on maximal diastolic potential suggested that intracellular loading with TEA had no effect on the time-independent "background" outward current (IK1). If we ascribe all observed TEA effects to the reduction of time dependent slow outward current Ix1, we can propose a hypothesis concerning the role of Ix1 in the regulation of APD at slow heart rates.
用20 mM氯化铵四乙铵（TEA）通过标本的切断端扩散进行细胞内加载，可延长犬浦肯野纤维的动作电位持续时间（APD），而不改变最大舒张电位、超射和最大除极速率（dV/dtmax）。在所有刺激频率下，APD均延长，但与正常规律相反，刺激间隔较长后APD的增加幅度大于较短刺激间隔后。在刺激频率突然改变后，TEA增加了达到新的稳态APD所需的搏动次数。细胞外钾浓度变化对最大舒张电位的影响表明，TEA细胞内加载对与时间无关的“背景”外向电流（IK1）没有影响。如果我们将所有观察到的TEA效应归因于时间依赖性慢外向电流Ix1的减少，我们可以提出一个关于Ix1在慢心率下APD调节中作用的假说。
