Du Yixing, Ma Baofeng, Kiyoshi Conrad M, Alford Catherine C, Wang Wei, Zhou Min
Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, Ohio; Department of Neurology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China; and.
Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, Ohio;
J Neurophysiol. 2015 Jun 1;113(10):3744-50. doi: 10.1152/jn.00206.2015. Epub 2015 Mar 25.
Mature astrocytes exhibit a linear current-to-voltage K(+) membrane conductance (passive conductance) and an extremely low membrane resistance (Rm) in situ. The combination of these electrophysiological characteristics establishes a highly negative and stable membrane potential that is essential for basic functions, such as K(+) spatial buffering and neurotransmitter uptake. However, astrocytes are coupled extensively in situ. It remains to be determined whether the observed passive behavior and low Rm are attributable to the intrinsic properties of membrane ion channels or to gap junction coupling in functionally mature astrocytes. In the present study, freshly dissociated hippocampal tissues were used as a new model to examine this basic question in young adult animals. The morphologically intact single astrocytes could be reliably dissociated from animals postnatal day 21 and older. At this animal age, dissociated single astrocytes exhibit passive conductance and resting membrane potential similar to those exhibited by astrocytes in situ. To precisely measure the Rm from single astrocytes, dual-patch single-astrocyte recording was performed. We show that dissociated single astrocytes exhibit a low Rm similarly to syncytial coupled astrocytes. Functionally, the symmetric expression of high-K(+) conductance enabled rapid change in the intracellular K(+) concentrations in response to changing K(+) drive force. Altogether, we demonstrate that freshly dissociated tissue preparation is a highly useful model for study of the functional expression and regulation of ion channels, receptors, and transporters in astrocytes and that passive behavior and low Rm are the intrinsic properties of mature astrocytes.
成熟的星形胶质细胞在原位表现出线性的电流-电压钾离子膜电导（被动电导）和极低的膜电阻（Rm）。这些电生理特性的组合建立了一个高度负性且稳定的膜电位，这对于诸如钾离子空间缓冲和神经递质摄取等基本功能至关重要。然而，星形胶质细胞在原位广泛耦合。目前尚不清楚观察到的被动行为和低Rm是归因于膜离子通道的内在特性还是功能成熟的星形胶质细胞中的缝隙连接耦合。在本研究中，新鲜解离的海马组织被用作一种新模型，以研究成年幼龄动物中的这个基本问题。形态完整的单个星形胶质细胞可以从出生后第21天及以上的动物中可靠地解离出来。在这个动物年龄，解离的单个星形胶质细胞表现出与原位星形胶质细胞相似的被动电导和静息膜电位。为了精确测量单个星形胶质细胞的Rm，进行了双膜片单星形胶质细胞记录。我们发现，解离的单个星形胶质细胞与合胞体耦合的星形胶质细胞一样表现出低Rm。在功能上，高钾离子电导的对称表达使得细胞内钾离子浓度能够响应变化的钾离子驱动力而快速变化。总之，我们证明新鲜解离的组织制备是研究星形胶质细胞中离子通道、受体和转运体的功能表达和调节的一个非常有用的模型，并且被动行为和低Rm是成熟星形胶质细胞的内在特性。
