Astrocytic gap junction blockade markedly increases extracellular potassium without causing seizures in the mouse neocortex
Astrocytic gap junction blockade markedly increases extracellular potassium without causing seizures in the mouse neocortex
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DOI：
10.1016/j.nbd.2016.12.017
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发表时间：
2017-05-01
影响因子：
6.1
通讯作者：
Carlen, Peter L.
中科院分区：
文献类型：
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作者：
Bazzigaluppi, Paolo;Weisspapir, Iliya;Carlen, Peter L.
细胞外钾浓度[K+]（0）是神经元兴奋性的主要决定因素。在健康的大脑中，[K+]（0）水平受到严格控制。在癫痫发作期间，[K+]（0）增加至15 mM，并被认为是由于其去极化效应而引起癫痫发作。虽然星形胶质细胞已被认为是通过连接蛋白43（Cx43）为基础的间隙连接（GJs）在多余的K+的再分配（或空间缓冲）中发挥关键作用，这种动态调节过程和癫痫发作之间的关系仍然未知。在这里，我们通过研究GJ和半通道阻断剂对体内[K+]（0）调节的影响，对比了星形胶质细胞GI和半通道的作用。[K+]（0）用K+敏感微电极测定。神经元的兴奋性估计的局部场电位（LFP）的反应，前爪刺激和静息状态活动的功率的变化。从1.61 +/- 0.3 mM的基线[K+]（0）水平开始，皮质显微注射CBX（一种广谱连接蛋白通道阻滞剂）增加[K+]（0）。到11 +/- 3 mM，Cx43 GJ/半通道阻断剂Gap 27将其从1.9 +/- 0.7增加到9 1 mM。在这些[K+]（0）水平下，未观察到癫痫发作。用TAT-Gap 19阻断Cx43半通道仅使[K+]（0）增加了~ 1 mM。微量注射4-氨基吡啶（一种已知的惊厥药）使[K+]增加。至-10 mM，并诱导自发复发性癫痫发作，而直接应用K+并不触发癫痫发作活动。这些发现是首次在体内证明星形胶质细胞GJ是[K+]（0）-10空间缓冲的主要决定因素，并且单独增加[K+]（0）不会引发新皮层癫痫发作。(C)2016 Elsevier Inc. All rights reserved.
Extracellular potassium concentration,[K+](0), is a major determinant of neuronal excitability. In the healthy brain, [K+](0) levels are tightly controlled. During seizures, [K+](0) increases up to 15 mM and is thought to cause seizures due to its depolarizing effect. Although astrocytes have been suggested to play a key role in the redistribution (or spatial buffering) of excess K+ through Connexin-43 (Cx43)-based Gap Junctions (GJs), the relation between this dynamic regulatory process and seizure generation remains unknown. Here we contrasted the role of astrocytic GIs and hemichannels by studying the effect of GJ and hemichannel blockers on [K+](0), regulation in vivo. [K+](0) was measured by K+-sensitive microelectrodes. Neuronal excitability was estimated by local field potential (LFP) responses to forepaw stimulation and changes in the power of resting state activity. Starting at the baseline [K+](0) level of 1.61 +/- 0.3 mM, cortical microinjection of CBX, a broad spectrum connexin channel blocker, increased [K+](0). to 11 +/- 3 mM, Cx43 GJ/hemichannel blocker Gap27 increased it from 1.9 +/- 0.7 to 9 1 mM. At these [K+](0) levels, no seizures were observed. Cx43 hemichannel blockade with TAT-Gap19 increased [K+](0) by only-1 mM. Microinjection of 4-aminopyridine, a known convulsant, increased [K+]. to-10 mM and induced spontaneously recurring seizures, whereas direct application of K+ did not trigger seizure activity. These findings are the first in vivo demonstration that astrocytic GJs are major determinants for the spatial buffering of [K+](0)-10 and that an increase in [K+](0) alone does not trigger seizures in the neocortex. (C) 2016 Elsevier Inc. All rights reserved.