Voltage-gated K+ channels in layer 5 neocortical pyramidal neurones from young rats:: subtypes and gradients
Voltage-gated K+ channels in layer 5 neocortical pyramidal neurones from young rats:: subtypes and gradients
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DOI：
10.1111/j.1469-7793.2000.00621.x
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发表时间：
2000-06-15
影响因子：
5.5
通讯作者：
Sakmann, B
中科院分区：
文献类型：
--
作者：
Korngreen, A;Sakmann, B
1. 我们研究了幼鼠（出生后13-15天）急性脑片中第5层（L5）新皮质锥体神经元的体细胞和顶树突中电压门控K+通道的类型和分布。有核斑块存在缓慢失活的外向K+电流和快速失活的外向K+电流。慢速K+电流被四乙基铵（TEA）完全阻断，IC50为5 +/- 1 mM（平均+/- S.E.M.），被4-氨基吡啶（4-AP）部分阻断。快速K+电流被4-AP阻断，IC50为4.2 +/- 0.5 mM，但没有被tea阻断。慢K+电流的活化动力学用二阶霍奇金-赫胥黎模型描述。慢速K+电流呈双指数失活。激活的四阶霍奇金-赫胥黎模型和失活的一阶模型描述了快速K+电流的动力学。在体细胞附体记录中，根据其单一的电导和失活动力学，可以区分出3类单一的K+通道：电导为13 +/- 1 pS的快速失活通道，电导为9.5 +/- 0.5 pS的慢速失活通道，电导为16 +/- 1 pS的非常慢速失活通道。慢速和极慢速K+通道的失活时间常数与成核斑块中观察到的慢速K+电流的失活时间常数相对应。这表明两个不同的K+通道介导了成核斑块中缓慢的K+电流。在体细胞记录中观察到的三种K+通道亚型沿着顶端树突存在。随着离体细胞距离的增加，细胞附着斑块中K+电流的振幅沿顶端树突减小，斜率为-0.9 +/- 0.3 pA / 100 mu m.7。结果表明，沿L5锥体神经元顶端树突的胞体电压门控K+通道密度的降低有助于确定树突再生电位起始的远端低阈值区域。
1. We investigated the types and distribution of voltage-gated K+ channels in the soma and apical dendrite of layer 5 (L5) neocortical pyramidal neurones, of young rats (postnatal days 13-15), in acute brain slices.2. A slow inactivating outward K+ current and a fast inactivating outward K+ current were detected in nucleated patches. The slow K+ current was completely blocked by tetraethylammonium (TEA) with an IC50 of 5 +/- 1 mM (mean +/- S.E.M.) and was partially blocked by 4-aminopyridine (4-AP). The fast K+ current was blocked by 4-AP with an IC50 of 4.2 +/- 0.5 mM, but was not blocked by TEA.3. The activation kinetics of the slow K+ current were described by a second order Hodgkin-Huxley model. The slow K+ current displayed bi-exponential inactivation. A fourth order Hodgkin-Huxley model for activation and first order for inactivation described the kinetics of the fast K+ current.4. In somatic cell-attached recordings, three classes of single K+ channels could be differentiated based on their unitary conductance and inactivation kinetics, a fast inactivating channel having a conductance of 13 +/- 1 pS, a slow inactivating channel having a conductance of 9.5 +/- 0.5 pS, and a very slowly inactivating channel having a conductance of 16 +/- 1 pS.5. The inactivation time constants of the slow and of the very slow K+ channel corresponded to the two inactivation time constants of the slow K+ current observed in nucleated patches. This suggested that two distinct K+ channels mediated the slow K+ current in nucleated patches.6. The three subtypes of K+ channels that were observed in somatic recordings were present along the apical dendrite. The amplitude of ensemble K+ currents in cell-attached patches decreased along the apical dendrite as the distance from the soma increased, with a slope of -0.9 +/- 0.3 pA per 100 mu m.7. The results suggest that the decrease of the voltage-gated K+ channel density from the soma along the apical dendrite of L5 pyramidal neurones helps to define a distal, low threshold region for the initiation of dendritic regenerative potentials.