Glial Maintenance of Local K+ and Neurotransmission

描述(由申请人提供)：神经元兴奋性和突触通讯受到细胞外K+([K+]o)轻微增加的抑制。在中风、脑损伤和癫痫发作期间，会出现大量的[K+]o升高，导致神经元缺陷。在正常和病理生理条件下，中枢神经系统中的星形胶质细胞通过被动机制协助缓冲[K+]o，这一机制尚不清楚。内向整流性K+通道(KIRS)被认为是导致被动K+稳态的原因，并由海马星形胶质细胞表达。这项提议将回答有关海马区星形胶质细胞KIRS的内源性功能的基本问题。星形胶质细胞膜片钳记录将决定Ba2+敏感刺激诱发的K+电流的生理特性。共聚焦显微镜和免疫细胞化学将被用来确定KIR在海马星形胶质细胞膜上的定位。膜片钳记录星形胶质细胞的胞体和突起，结合K+成像技术，将确定KIR响应神经元刺激而携带局部内向K+电流的能力。这些研究将确定KIRS在海马星形胶质细胞中的功能相关性，并为KIRS在被动[K+]o缓冲中的作用提供新的见解。

DESCRIPTION (provided by applicant): Neuronal excitability and synaptic communication are depressed by mild increases in extracellular K+ ([K+]o). During stroke, brain trauma, and seizures, large [K+]o rises occur, causing neuronal deficits. Under normal and pathophysiological conditions, astrocytes in the CNS assist in buffering [K+]o by passive mechanisms that are not well understood. Inwardly-rectifying K+ channels (KIRs) are thought to be responsible for passive K+ homeostasis, and are expressed by hippocampal astrocytes. This proposal will answer fundamental questions concerning the endogenous function of astrocyte KIRs in the hippocampus. Astrocyte patch-clamp recordings will determine the physiological properties of barium-sensitive stimulus evoked K+ currents. Confocal microscopy and immunocytochemistry will be used to determine the localization of KIRs on hippocampal astrocyte membranes. Patch-clamp recordings from astrocyte somas and processes, along with K+ imaging techniques, will determine the capacity for KIRs to carry localized inward K+ currents in response to neuronal stimulation. These studies will determine the functional relevance of KIRs in hippocampal astrocytes and provide new insight into the role of KIRs in passive [K+]o buffering.