Coraboeuf E, Carmeliet E
Pflugers Arch. 1982 Feb;392(4):352-9. doi: 10.1007/BF00581631.
Voltage clamp analysis of the transient outward (positive dynamic) current was performed in sheep Purkinje fibers at a pulse frequency of 1/min. 4-aminopyridine (4-AP, 1 mM) suppressed most of the transient outward current, thus revealing the slow inward current, isi, and an associated brief outward current ibo. The long lasting component of the current suppressed by 4-AP was labelled ilo. In the presence of 4-AP, ibo was suppressed either by caffeine 10 mM or when Sr was substituted for Ca, both conditions making isi clearly detectable. Mn ions suppressed both isi and ibo. Current decay was a monoexponential process for ibo (tau = 12 ms) and a two exponential process for ilo (tau 1 = 80-100 ms, tau 2 = 250-400 ms). The peak amplitude-Em relationships were different for the two currents. It was shown that the reversal potential of ilo was not measurable by the usual method probably because of the too fast activation-deactivation kinetics of the current. It is concluded that not one but two transient outward currents with different electrophysiological and pharmacological characteristics exist in the sheep Purkinje fiber. The reason of the caffeine-sensitivity of ibo is discussed.
在绵羊浦肯野纤维中，以1次/分钟的脉冲频率对瞬时外向（正动态）电流进行电压钳分析。4-氨基吡啶（4-AP，1 mM）抑制了大部分瞬时外向电流，从而揭示了缓慢内向电流isi以及相关的短暂外向电流ibo。被4-AP抑制的电流的持久成分标记为ilo。在存在4-AP的情况下，10 mM咖啡因或用Sr替代Ca时，ibo均被抑制，这两种情况都使isi清晰可测。锰离子抑制isi和ibo。对于ibo，电流衰减是单指数过程（时间常数tau = 12 ms），对于ilo是双指数过程（tau 1 = 80 - 100 ms，tau 2 = 250 - 400 ms）。两种电流的峰值幅度与膜电位（Em）关系不同。结果表明，由于电流的激活 - 失活动力学太快，通常方法无法测量ilo的反转电位。得出的结论是，绵羊浦肯野纤维中存在的不是一种而是两种具有不同电生理和药理学特性的瞬时外向电流。文中讨论了ibo对咖啡因敏感的原因。
