Abstract:

Astrocytic Kir4.1 channels and spatial potassium buffering: Astrocytes play a crucial role in maintaining the structural and functional integrity of the brain, which includes formation of the blood-brain barrier, maintenance of water and ion homeostasis, metabolism of neurotransmitters and secretion of various neuroactive molecules. Among these functions, spatial potassium (K+) buffering by astrocytes is an essential system for controlling extracellular K+ concentration ([K+]o) and neuronal . Neurons normally release considerable amounts of K+ during the repolarization phase of an action potential. At tripartite synapses, a single action potential elevates the local [K+]o level by about 1 mM and, if uncorrected, [K+]o reaches 10 mM or more, causing abnormal discharges and finally spreading depression.Spatial K+ buffering by astrocytes is a K+-clearance system which removes an excess of extracellular K+ and transports it to the regions of low [K+]o such as capillary vessels . In addition,the spatial K+ buffering system is coupled to astrocytic glutamate uptake by glutamate transporters (e.g., EAAT1 and EAAT2) and water transport by aquaporin-4 (AQP4)