Jabs Ronald, Matthias Katja, Grote Alexander, Grauer Michael, Seifert Gerald, Steinhäuser Christian
Institute of Cellular Neurosciences, Medical School, University of Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany.
Glia. 2007 Dec;55(16):1648-55. doi: 10.1002/glia.20580.
Purinergic signalling plays a major role in intercellular communication between neurons and glial cells. Glial cells express metabotropic receptors for ATP and adenosine, the latter being activated after ATP cleavage through extracellular ecto-ATPase activity. Ionotropic receptors for extracellular ATP, so called P2X receptors, might contribute to neuron-glia signalling. However, experimental evidence for the presence of these receptors in glial cells is less convincing so far. In a previous study, immunohistochemistry was used to identify P2X(1-4,6,7) receptor protein in S100beta-positive hippocampal glial cells. Applying patch clamp and fast application techniques, here we challenged the question of the functional expression of these receptors. Time correlated membrane currents served as test criterion for receptor function, since P2X receptor activation leads to the opening of unspecific cation channels in a millisecond time scale. Agonists were applied via short pressure puffs, with a fast concentration clamp method and through UV flash triggered photolysis of caged ATP. Two types of murine hippocampal macroglial cells, both labelled by the expression of green fluorescence protein driven by the human glial fibrillary acid protein promoter, were analysed in acute brain slices and in freshly dissociated cell suspensions. Surprisingly, ATP or related agonists completely failed to activate currents. Additionally, changes in spontaneously occurring glial postsynaptic currents were never observed. These results have been verified using rat and human hippocampal tissue as well as investigating cells from P2X7 knock out mice. It is concluded that in acute preparations, astroglial cells of the hippocampal CA1 subfield do not express functional P2X receptors.
嘌呤能信号传导在神经元与神经胶质细胞之间的细胞间通讯中起主要作用。神经胶质细胞表达ATP和腺苷的代谢型受体，后者在ATP通过细胞外ecto - ATP酶活性裂解后被激活。细胞外ATP的离子型受体，即所谓的P2X受体，可能参与神经元 - 神经胶质细胞信号传导。然而，迄今为止，这些受体在神经胶质细胞中存在的实验证据尚不令人信服。在先前的一项研究中，免疫组织化学被用于鉴定S100β阳性海马神经胶质细胞中的P2X(1 - 4,6,7)受体蛋白。在此，我们应用膜片钳和快速施加技术来探讨这些受体的功能表达问题。时间相关的膜电流作为受体功能的测试标准，因为P2X受体激活会在毫秒时间尺度上导致非特异性阳离子通道开放。激动剂通过短压力脉冲、快速浓度钳制方法以及紫外线闪光触发的笼状ATP光解来施加。在急性脑片和新鲜解离的细胞悬液中分析了两种由人类胶质纤维酸性蛋白启动子驱动的绿色荧光蛋白表达标记的小鼠海马大胶质细胞。令人惊讶的是，ATP或相关激动剂完全未能激活电流。此外，从未观察到自发发生的神经胶质细胞突触后电流的变化。这些结果已使用大鼠和人类海马组织以及对P2X7基因敲除小鼠的细胞进行研究得到验证。得出的结论是，在急性制剂中，海马CA1亚区的星形胶质细胞不表达功能性P2X受体。
