Reduction in potassium currents in identified cutaneous afferent dorsal root ganglion neurons after axotomy
Reduction in potassium currents in identified cutaneous afferent dorsal root ganglion neurons after axotomy
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DOI：
10.1152/jn.1999.82.2.700
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发表时间：
1999-08-01
影响因子：
2.5
通讯作者：
Kocsis, JD
中科院分区：
文献类型：
--
作者：
Everill, B;Kocsis, JD
钾电流在调节神经元兴奋性方面起着重要作用。本实验观察了切断背根神经节对皮肤传入背根节(DRG)神经元三种电压激活性钾电流的影响。坐骨神经切断后14~21d，L-4和L-5背根神经节神经元急性分离，接种后2~8h观察。从已鉴定的皮肤传出神经元(直径46-50微米)获得全细胞膜片钳记录，用适当的离子替代和通道阻断剂阻断Na+和Ca~(2+)电流来分离K~+电流。电流分量的分离是基于对树突毒素或4-氨基吡啶的敏感性以及对调节电压变化的响应。对照神经元和损伤神经元都表现出由不同的动力学和药理成分组成的性质相似的复合钾电流。三个不同的K+电流成分，一个持续的(I-K)和两个瞬时的(I-A和I-D)，按不同的比例被识别出来。然而，与对照细胞相比，切断轴突的细胞的总峰电流降低了52%。结扎后两个电流分量较对照细胞减少，I-A减少60%，I-K减少65%以上。I，急性结扎后未受影响。这些结果表明，大的皮肤传入神经元在神经结扎后，由于I-K和I-A的减少，总的K+电流显著减少，这可能与受损初级传入神经元的兴奋性变化有关。
Potassium currents have an important role in modulating neuronal excitability. We have investigated the effects of axotomy on three voltage-activated K+ currents, one sustained and two transient, in cutaneous afferent dorsal root ganglion (DRG) neurons. Fourteen to 21 days after axotomy, L-4 and L-5 DRG neurons were acutely dissociated and were studied 2-8 h after plating. Whole cell patch-clamp recordings were obtained from identified cutaneous efferent neurons (46-50 mu m diam); K+ currents were isolated by blocking Na+ and Ca2+ currents with appropriate ion replacement and channel blockers. Separation of the current components was achieved on the basis of sensitivity to dendrotoxin or 4-aminopyridine and by the response to variation in conditioning voltage. Both control and injured neurons displayed qualitatively similar complex K+ currents composed of distinct kinetic and pharmacological components. Three distinct K+ current components, a sustained (I-K) and two transient (I-A and I-D), were identified in variable proportions. However, total peak current was reduced by 52% in the axotomized cells when compared with control cells. Two current components were reduced after ligation, I-A by 60%, I-K by over 65%, compared with control cells. I, appeared unaffected after acute ligation. These results indicate a large reduction in overall K+ current, resulting from reductions in I-K and I-A, on large cutaneous afferent neurons after nerve ligation and have implications for excitability changes of injured primary afferent neurons.