Homogeneous distribution of large-conductance calcium-dependent potassium channels on soma and apical dendrite of rat neocortical layer 5 pyramidal neurons
Homogeneous distribution of large-conductance calcium-dependent potassium channels on soma and apical dendrite of rat neocortical layer 5 pyramidal neurons
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DOI：
10.1111/j.1460-9568.2005.03934.x
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发表时间：
2005-02-01
影响因子：
3.4
通讯作者：
Berger, T
中科院分区：
文献类型：
--
作者：
Benhassine, N;Berger, T
第5层锥体神经元树突上的电压门控电导参与突触整合和输出产生。我们调查的性质和分布的大电导钙激活钾通道（BK通道）在这种细胞类型中使用切除补丁急性切片制备大鼠体感皮层。BK通道的特点是电导大，对特异性阻断剂paxilline和iberiotoxin敏感。BK通道表现出明显的钙依赖性，最大开放概率为0.69在10 μ m和0.42在3 μ m游离钙。它们的打开概率和打开和关闭状态之间的过渡时间常数是电压依赖性的。在去极化电位下，BK通道门控由两个打开状态和一个关闭状态描述。去极化由于打开时间常数的延长和关闭时间常数的缩短而增加打开概率。体细胞和树突状BK通道的钙依赖性和生物物理特性是相同的。免疫荧光显示第5层锥体神经元的顶树突上存在BK通道。膜片钳记录显示，在索马和沿着顶端树突上的BK通道密度均匀，高达850 μ m，平均密度为1.9个通道/μ m（2）。BK通道可以单独表达，也可以在含有多达四个通道的簇中表达。这项研究表明存在的BK通道的树突。它们的激活可能会调节钠和钙动作电位的形状，它们的传播沿着树突，从而在躯体和树突动作电位起始区之间的电紧张距离。
Voltage-gated conductances on dendrites of layer 5 pyramidal neurons participate in synaptic integration and output generation. We investigated the properties and the distribution of large-conductance calcium-activated potassium channels (BK channels) in this cell type using excised patches in acute slice preparations of rat somatosensory cortex. BK channels were characterized by their large conductance and sensitivity to the specific blockers paxilline and iberiotoxin. BK channels showed a pronounced calcium-dependence with a maximal opening probability of 0.69 at 10 mu m and 0.42 at 3 mu m free calcium. Their opening probability and transition time constants between open and closed states are voltage-dependent. At depolarized potentials, BK channel gating is described by two open and one closed states. Depolarization increases the opening probability due to a prolongation of the open time constant and a shortening of the closed time constant. Calcium-dependence and biophysical properties of somatic and dendritic BK channels were identical. The presence of BK channels on the apical dendrite of layer 5 pyramidal neurons was shown by immunofluorescence. Patch-clamp recordings revealed a homogeneous density of BK channels on the soma and along the apical dendrite up to 850 mu m with a mean density of 1.9 channels per mu m(2). BK channels are expressed either isolated or in clusters containing up to four channels. This study shows the presence of BK channels on dendrites. Their activation might modulate the shape of sodium and calcium action potentials, their propagation along the dendrite, and thereby the electrotonic distance between the somatic and dendritic action potential initiation zones.