Activation of heteromeric G protein-gated inward rectifier K+ channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons
Activation of heteromeric G protein-gated inward rectifier K+ channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons
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DOI：
10.1073/pnas.94.13.7070
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发表时间：
1997-06-24
影响因子：
11.1
通讯作者：
Davidson, N
中科院分区：
文献类型：
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作者：
Ehrengruber, MU;Doupnik, CA;Davidson, N
G蛋白门控内向整流钾通道亚基1-4（GIRK 1 -4）是从神经元和心房组织中克隆的功能异源四聚体。为了研究GIRK对神经元兴奋的抑制作用，我们在培养的18天大鼠胚胎海马神经元中过表达GIRK，这些神经元通常缺乏或显示少量的GIRK蛋白和电流。GIRK 1 +2和GIRK 1 +4共感染神经元后，内源性GABA（B）、5-HT 1A和腺苷A1受体均可激活GIRK电流。在电流钳条件下，GIRK激活可使细胞膜电导增加1 ~ 2倍，使细胞超极化11-14 mV，抑制动作电位放电bg增加，使放电阈值电流增加2 ~ 3倍。这些作用在未感染和模拟感染的神经元中均未发现，与M受体激动剂刺激心房肌细胞天然GIRK电流的作用相似。从实验数据中模拟了GIRK激活的两种抑制效应：超极化和去极化脉冲的减少。这些抑制作用在静息膜电位和电压门控Na+和K+电流被激活的电位之间的电压范围内具有生理重要性;这是GIRK电流向外的地方。
G protein-gated inward rectifier K+ channel subunits 1-4(GIRK1-4) have been cloned from neuronal and atrial tissue and function as heterotetramers, To examine the inhibition of neuronal excitation by GIRKs, we overexpressed GIRKs in cultured hippocampal neurons from 18 day rat embryos, which normally lack or show low amounts of GIRK protein and currents. Adenoviral recombinants containing the cDNAs for GIRK1, GIRK2, GIRK4, and the serotonin 1A receptor were constructed, Typical GIRK currents could be activated by endogenous GABA(B), serotonin 5-HT1A, and adenosine A1 receptors in neurons coinfected with GIRK1+2 or GIRK1+4. Under current clamp, GIRK activation increased the cell membrane conductance by 1- to 2-fold, hyperpolarized the cell by 11-14 mV,and inhibited action potential firing bg increasing, the threshold current for firing by 2- to 3-fold, These effects were not found in non- and mock-infected neurons, and were similar to the effects of muscarinic stim ulation of native GIRK currents in atrial myocytes. Two inhibitory effects of GIRK activation, hyperpolarization and diminution of depolarizing pulses, were simulated from the experimental data. These inhibitory effects are physiologically important in the voltage range between the resting membrane potential and the potential where voltage-gated Na+ and K+ currents are activated; that is where GIRK currents are outward.