大鼠海马脑片星形胶质细胞与NG2胶质细胞形态学及电生理特性比较

目的:比较研究大鼠海马脑片星形胶质细胞和NG2胶质细胞(以下简称NG2细胞)的形态学特点和电生理特性,为区别这两种胶质细胞提供依据,也为进一步研究两者的功能及相互关系等提供实验基础。方法:以P21～P25大鼠海马CA1区放射层胶质细胞为研究对象,通过脑片钳全细胞记录、记录后染色标记以及激光共聚焦成像等技术方法,比较星形胶质细胞与NG2细胞在形态学和电生理学特性上的异同。结果:形态学上,星形胶质细胞具有大量的突起,并且突起呈丛状分支,极细的突起非常发达,形成海绵样结构;NG2细胞也具有较多突起,但突起分支较少,突起呈长线状延伸出较长的距离,往往缺少星形胶质细胞典型的一个或多个粗大的一级突起。电生理特性上,两种细胞的静息膜电位(RMP)非常接近,而膜电容(Cm)和膜电阻(Rm)则差异非常大。对于星形胶质细胞,其I-V曲线呈线性,电流没有任何整流现象;而NG2细胞I-V曲线具有明显的外向整流特性,表达大量的快钾通道电流(Ka)、延迟整流钾电流(Kdr),以及比较小的内向整流钾电流(Kir);而且部分NG2细胞还表达低密度的电压依赖性钠电流。结论:大鼠海马脑片星形胶质细胞和NG2细胞在形态学和电生理上均存在一定的差异;在脑片钳实验中,根据这些差异,可以清楚地区分两者。

Comparative Studies on the Morphological and Basic Electrophysiological Properties of Astrocytes and NG2 Glial Cells in Rat Hippocampal Slices

Objective:The morphological and electrophysiological characteristics of astrocytes and NG2 glia in rat hippocampal slices have been investigated in order to distinguish these two types of glial cells.Methods:All the recorded cells came from CA1 stratum radiatum(SR) regions in P21～P25 rat hippocampal slices.By employing patch clamp whole-cell recording technique,post-recording labeling method and confocal imaging system,we have studied the differences between astrocytes and NG2 glial cells in the morphological and basic electrophysiological properties.Results:Morphometrically,astrocytes harbored a large number of fine processes which were extremely dense and branched.Abundant processes formed the typical spongiform morphology of astrocytes.In comparison,NG2 glia had much less branched processes that were long and threadlike.The somata of NG2 cells were small and round and,unlike astorcytes,lack of classic primary processes.Electrophysiologically,the resting membrane potential(RMP) of these two types of glial cells were very close.However,the differences in the membrane capacitance(Cm) and membrane resistance(Rm) were significant.I-V relationship from astrocytes was linear which signified the typical passive electrical character of astrocytes,but I-V plot from NG2 glia showed apparent rectification.Fast-inactiving K+ currents(Ka),delayed rectifying K+ currents(Kdr) and a fraction of inwardly rectifying K+ currents(Kir) had contributed to the whole-cell currents of NG2 glia.In addition,some of NG2 glia expressed voltage-gated Na+ currents in a low density.Conclusion:Astrocytes and NG2 glial cells have different morphological and electrophysiological properties and based on the above-mentioned differences we can distinguish them very clearly.