Kv2 subunits underlie slowly inactivating potassium current in rat neocortical pyramidal neurons
Kv2 subunits underlie slowly inactivating potassium current in rat neocortical pyramidal neurons
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DOI：
10.1113/jphysiol.2007.128454
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发表时间：
2007-06-15
影响因子：
5.5
通讯作者：
Foehring, R. C.
中科院分区：
文献类型：
--
作者：
Guan, D.;Tkatch, T.;Foehring, R. C.
我们确定了大鼠躯体感觉和运动皮层Kv 2通道亚单位的表达，并测试了Kv 2亚单位对颗粒上锥体神经元缓慢失活K+电流的贡献。单细胞RT-PCR结果显示，几乎所有的锥体细胞表达Kv2.1 mRNA，约80%的锥体细胞表达Kv2.2 mRNA。免疫细胞化学显示Kv2.1和Kv2.2亚基的分布存在显著差异。Kv2.1亚基分布于锥体细胞的胞体和近端树突上。Kv2.2亚基主要分布在深层锥体细胞亚群的大顶枝上。我们使用了两种方法来隔离电流通过Kv 2通道后，排除Kv 1亚基的贡献：细胞内扩散的Kv2.1抗体通过记录移液管和细胞外应用rStromatoxin-1（ScTx）。Kv2.1抗体特异性阻断缓慢失活的K+电流25-50%（8分钟），表明Kv2.1亚基是新皮质锥体神经元中大部分电流的基础。ScTx（300 nM）也抑制了40%的缓慢失活K+电流。我们观察到Kv2.1抗体和ScTx的作用之间的闭塞。此外，Kv2.1抗体和ScTx敏感的电流表现出类似的恢复失活和电压依赖性和动力学的激活和失活。这些数据表明，两种药物靶向相同的通道。考虑到Kv2.1和2.2亚基的定位，来自截短的解离细胞的电流可能由Kv2.1亚基主导。与表达系统中的Kv2.1电流相比，新皮层锥体细胞中的Kv2.1电流在相对负的电位下激活和失活，并且对保持电位非常敏感。
We determined the expression of Kv2 channel subunits in rat somatosensory and motor cortex and tested for the contributions of Kv2 subunits to slowly inactivating K+ currents in supragranular pyramidal neurons. Single cell RT-PCR showed that virtually all pyramidal cells expressed Kv2.1 mRNA and similar to 80% expressed Kv2.2 mRNA. Immunocytochemistry revealed striking differences in the distribution of Kv2.1 and Kv2.2 subunits. Kv2.1 subunits were clustered and located on somata and proximal dendrites of all pyramidal cells. Kv2.2 subunits were primarily distributed on large apical dendrites of a subset of pyramidal cells from deep layers. We used two methods for isolating currents through Kv2 channels after excluding contributions from Kv1 subunits: intracellular diffusion of Kv2.1 antibodies through the recording pipette and extracellular application of rStromatoxin-1 (ScTx). The Kv2.1 antibody specifically blocked the slowly inactivating K+ current by 25-50% (at 8 min), demonstrating that Kv2.1 subunits underlie much of this current in neocortical pyramidal neurons. ScTx (300 nM) also inhibited similar to 40% of the slowly inactivating K+ current. We observed occlusion between the actions of Kv2.1 antibody and ScTx. In addition, Kv2.1 antibody- and ScTx-sensitive currents demonstrated similar recovery from inactivation and voltage dependence and kinetics of activation and inactivation. These data indicate that both agents targeted the same channels. Considering the localization of Kv2.1 and 2.2 subunits, currents from truncated dissociated cells are probably dominated by Kv2.1 subunits. Compared with Kv2.1 currents in expression systems, the Kv2.1 current in neocortical pyramidal cells activated and inactivated at relatively negative potentials and was very sensitive to holding potential.