Spatial buffering of potassium ions in brain extracellular space
Spatial buffering of potassium ions in brain extracellular space
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DOI：
10.1016/s0006-3495(00)76822-6
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发表时间：
2000-06-01
影响因子：
3.4
通讯作者：
Nicholson, C
中科院分区：
文献类型：
--
作者：
Chen, KC;Nicholson, C
长期以来，人们一直认为脑细胞外空间中局部钾梯度消散的一个重要机制是所谓的空间缓冲，通常与神经胶质细胞有关。然而，迄今为止，还没有分析描述的K+清除率的特征模式介导的这样一种机制。本研究重新分析了Gardner-Medwin（1983，J. Physiol.（Lond.）335：393-426），以前已经解决了数字。在适当的近似下，导出了有限平行区域内神经胶质细胞钾离子浓度和相应膜电位的瞬态解。详细的二室模型的数值模拟证实了分析结果。该模拟探讨了空间缓冲电流和细胞外K+对胶质细胞终足膜和非终足膜中内向整流K+通道分布、胶质细胞几何长度以及被动KCl摄取的影响的依赖性。将神经胶质细胞视为等效的漏电流电缆，分析表明，当神经胶质细胞的几何长度等于相应的电紧张空间常数时，端足电流最大。因此，长的神经胶质突起不适合用于空间缓冲，除非轴向空间常数可以匹配突起的长度。最后，本研究讨论了空间缓冲机制是否能够有效地运输K+的距离超过几个胶质细胞的空间常数。
It has long been assumed that one important mechanism for the dissipation of local potassium gradients in the brain extracellular space is the so-called spatial buffer, generally associated with glial cells. To date, however, there has been no analytical description of the characteristic patterns of K+ clearance mediated by such a mechanism. This study reanalyzed a mathematical model of Gardner-Medwin (1983, J. Physiol. (Lond.). 335:393-426) that had previously been solved numerically. Under suitable approximations, the transient solutions for the potassium concentrations and the corresponding membrane potentials of glial cells in a finite, parallel domain were derived. The analytic results were substantiated by numerical simulations of a detailed two-compartment model. This simulation explored the dependence of spatial buffer current and extracellular K+ on the distribution of inward rectifier K+ channels in the glial endfoot and nonendfoot membranes, the glial geometric length, and the effect of passive KCI uptake. Regarding the glial cells as an equivalent leaky cable, the analyses indicated that a maximum endfoot current occurs when the glial geometric length is equal to the corresponding electrotonic space constant. Consequently, a long glial process is unsuitable for spatial buffering, unless the axial space constant can match the length of the process. Finally, this study discussed whether the spatial buffer mechanism is able to efficiently transport K+ over distances of more than several glial space constants.