Ionic currents of solitary horizontal cells isolated from goldfish retina.
Ionic currents of solitary horizontal cells isolated from goldfish retina.
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DOI：
10.1113/jphysiol.1983.sp014981
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发表时间：
1983-12
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影响因子：
--
通讯作者：
M. Tachibana
中科院分区：
文献类型：
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作者：
M. Tachibana
从木瓜蛋白酶处理的金鱼视网膜上分离出来的孤立水平细胞会产生动作电位并显示出非线性电流-电压关系。通过单微电极电压钳技术分析了潜在的离子电导机制。药理学和离子替代实验表明，离子电流可以分为至少四种电压依赖性电流：Ca 电流和三种类型的 K 电流。 Ca 电流在超过 ‐45 mV 时被膜去极化激活，在接近 0 mV 时达到最大值，并在正电势更大时变得更小。通过外推，估计反转电位约为+50 mV。 Ca 电流因细胞内 Ca 离子的积累而失活，但不会因膜去极化而失活。 Co 离子 (4mM) 阻断了该电流。第一种类型的 K 电流在静息电位（相当于 ‐60 mV）附近表现出异常（内向）整流。从静止水平开始的超极化产生了一个大的、几乎稳定的内向电流，而去极化仅引起了一个小的、稳定的外向电流。电流-电压关系揭示了膜电位超过‐50 mV 时的浅负阻区域。电流被 Cs (10 mM) 或 Ba (1 mM) 离子阻挡。第二种类型的 K 电流（瞬时外向电流）由超过 ‐25 mV 的膜去极化激活。当膜去极化时，峰值幅度几乎呈指数增加。在稳定去极化期间，该电流呈指数衰减（+20 mV 时的时间常数等于 500 ms）。通过调节去极化（大于 10 秒）超过 ‐30 mV 使电流失活，并用 4-氨基吡啶 (10 mM) 阻断。第三种类型的 K 电流是维持的外向电流，它被超过 ‐20 mV 的膜去极化激活，在几百毫秒内增加到稳定水平，并且几乎没有失活。随着膜去极化，振幅增加。电流被四乙铵离子 (20 mM) 阻断。未检测到 Ca 介导的 K 电流。孤立水平细胞的动作电位和非线性电流-电压关系可以通过四种离子电流的组合来定性地解释。
Solitary horizontal cells, dissociated from papain‐treated goldfish retinas, produce action potentials and show a non‐linear current‐voltage relationship. Underlying ion‐conductance mechanisms were analysed by a single‐micro‐electrode voltage‐clamp technique. Pharmacological and ion‐substitution experiments revealed that ionic currents could be separated into at least four voltage‐dependent currents: a Ca current and three types of K currents. The Ca current was activated by membrane depolarization beyond ‐45 mV, reached a maximal value near 0 mV, and became smaller at more positive potentials. By extrapolation, the reversal potential was estimated to be approximately +50 mV. The Ca current was inactivated by accumulation of intracellular Ca ions but not by membrane depolarization. Co ions (4mM) blocked this current. The first type of K current showed anomalous (inward‐going) rectification near the resting potential (congruent to ‐60 mV). Hyperpolarization from the resting level produced a large, almost steady inward current, while depolarization evoked only a small, steady outward current. The current‐voltage relationship revealed a shallow negative resistance region at membrane potentials beyond ‐50 mV. The current was blocked by Cs (10 mM) or Ba (1 mM) ions. The second type of K current (the transient outward current) was activated by membrane depolarization beyond ‐25 mV. The peak amplitude increased almost exponentially as the membrane was depolarized. During steady depolarization this current decayed exponentially (time constant congruent to 500 ms at +20 mV). The current was inactivated by conditioning depolarization (greater than 10 s) beyond ‐30 mV and blocked by 4‐aminopyridine (10 mM). The third type of K current was the maintained outward current which was activated by membrane depolarization beyond ‐20 mV, increased to a steady level in a few hundred milliseconds, and showed little inactivation. The amplitude increased as the membrane was depolarized. The current was blocked by tetraethylammonium ions (20 mM). A Ca‐mediated K current was not detected. Action potentials and the non‐linear current‐voltage relationship of solitary horizontal cells can be explained qualitatively by the combination of the four ionic currents.