Space-clamp problems when voltage clamping neurons expressing voltage-gated conductances
Space-clamp problems when voltage clamping neurons expressing voltage-gated conductances
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DOI：
10.1152/jn.01232.2007
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发表时间：
2008-03-01
影响因子：
2.5
通讯作者：
Korngreen, Alon
中科院分区：
文献类型：
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作者：
Bar-Yehuda, Dan;Korngreen, Alon
电压钳技术仅适用于球形细胞。在非球形细胞中，例如神经元，膜电位在电压钳电极的远端不被钳位。这意味着电压钳电极记录的电流是局部电流和来自经历不同膜电位的位置的轴向电流的总和。此外，从非球形细胞记录的电压门控电流，根据定义，由于缺乏空间箝位而严重失真。在非球形细胞电压钳位的理由是，首先，缺乏空间钳是不严重的神经元短树突。第二，可以调用被动电缆理论来证明电压钳应用于分支神经元的合理性，这表明电位衰减足够浅以允许神经元的空间钳位。在这里，使用数值模拟，我们表明，电压门控的K+和Ca2+电流的失真是相当大的，即使在神经元短树突。模拟还表明，被动电缆理论不能用来证明电压钳位的神经元，由于显着分流的电压门控电导在通道激活过程中的反转电位。在大鼠躯体感觉皮层中使用体细胞和树突电压钳实验验证了模拟所做的一些预测。我们的研究结果表明，电压门控的K+和Ca2+电流记录从分支神经元几乎总是严重扭曲。
The voltage-clamp technique is applicable only to spherical cells. In nonspherical cells, such as neurons, the membrane potential is not clamped distal to the voltage-clamp electrode. This means that the current recorded by the voltage-clamp electrode is the sum of the local current and of axial currents from locations experiencing different membrane potentials. Furthermore, voltage-gated currents recorded from a nonspherical cell are, by definition, severely distorted due to the lack of space clamp. Justifications for voltage clamping in nonspherical cells are, first, that the lack of space clamp is not severe in neurons with short dendrites. Second, passive cable theory may be invoked to justify application of voltage clamp to branching neurons, suggesting that the potential decay is sufficiently shallow to allow spatial clamping of the neuron. Here, using numerical simulations, we show that the distortions of voltage-gated K+ and Ca2+ currents are substantial even in neurons with short dendrites. The simulations also demonstrate that passive cable theory cannot be used to justify voltage clamping of neurons due to significant shunting to the reversal potential of the voltage-gated conductance during channel activation. Some of the predictions made by the simulations were verified using somatic and dendritic voltage-clamp experiments in rat somatosensory cortex. Our results demonstrate that voltage-gated K+ and Ca2+ currents recorded from branching neurons are almost always severely distorted.