Zbicz K L, Weight F F
J Neurophysiol. 1985 Apr;53(4):1038-58. doi: 10.1152/jn.1985.53.4.1038.
Membrane currents activated by step changes in membrane potential were studied in hippocampal pyramidal neurons of region CA3 using the single microelectrode voltage-clamp technique. The transient outward current activated by depolarizing steps appeared to be composed of two transient currents that could be distinguished by differences in voltage sensitivity, time course, and pharmacological sensitivity. The more slowly decaying current was activated by voltage steps positive to -60 mV and declined exponentially with a time constant between 200 and 400 ms. This current inactivated as the holding potential was made more positive over the range of -75 to -45 mV and was 50% inactivated near -60 mV. The more slowly decaying transient current was selectively blocked by 0.5 mM 4-aminopyridine (4-AP) but not by 5-10 mM tetraethylammonium (TEA) or 2-5 mM Mn2+. The second transient current had a much faster time course than the 4-AP-sensitive current, having a duration of 5-20 ms. This very fast transient current was observed during potential steps positive to -45 mV. The fast transient current was inactivated when the holding potential was made positive to -45 mV. The amplitude of the fast transient current was greatly reduced by the application of 4 mM Mn2+ or Ca2+-free artificial cerebrospinal fluid (CSF). The fast transient current appeared to be unaffected by 0.5 mM 4-AP but was greatly reduced by 10 mM TEA. These results suggest that the transient outward current observed during depolarizing steps is composed of at least two distinct transient currents. The more slowly decaying current resembles the A-current originally described in molluscan neurons (9, 32, 42) in voltage sensitivity, time course, and pharmacological sensitivity. The faster transient current resembles a fast, Ca2+-dependent transient current previously observed in bull-frog sympathetic neurons (5, 27).
采用单微电极电压钳技术，对CA3区海马锥体细胞的膜电流进行了研究。去极化阶跃激活的瞬时外向电流似乎由两种瞬时电流组成，这两种电流可通过电压敏感性、时间进程和药理学敏感性的差异加以区分。衰减较慢的电流由高于 -60 mV的电压阶跃激活，并以200至400毫秒的时间常数呈指数衰减。当钳制电位在 -75至 -45 mV范围内更正时，该电流失活，在接近 -60 mV时50%失活。衰减较慢的瞬时电流被0.5 mM 4-氨基吡啶（4-AP）选择性阻断，但不被5 - 10 mM四乙铵（TEA）或2 - 5 mM Mn2+阻断。第二种瞬时电流的时间进程比4-AP敏感电流快得多，持续时间为5 - 20毫秒。在高于 -45 mV的电位阶跃期间可观察到这种非常快速的瞬时电流。当钳制电位高于 -45 mV时，快速瞬时电流失活。施加4 mM Mn2+或无Ca2+的人工脑脊液（CSF）可使快速瞬时电流的幅度大大降低。快速瞬时电流似乎不受0.5 mM 4-AP的影响，但被10 mM TEA大大降低。这些结果表明，去极化阶跃期间观察到的瞬时外向电流至少由两种不同的瞬时电流组成。衰减较慢的电流在电压敏感性、时间进程和药理学敏感性方面类似于最初在软体动物神经元中描述的A电流（9, 32, 42）。较快的瞬时电流类似于先前在牛蛙交感神经元中观察到的快速、Ca2+依赖的瞬时电流（5, 27）。
