Directed spatial potassium redistribution in rat neocortex

The functional role of the glial network as a draining system for extracell ular potassium (spatial buffer) was investigated in rat neocortical brain s lices. After electrical stimulation, extracellular space volume decreased i n the middle cortical layers and increased in the upper cortical layers, co nfirming predictions for a spatial buffer. The widening of extracellular sp ace was associated with an increase in extracellular potassium. The data su ggested a delayed redistribution of potassium from middle to superficial co rtical layers. Interruption of gap junctions abolished the widening of extr acellular space. The data show that a multicellular directed network connec ted by gap junctions participates in maintaining potassium homeostasis in b rain. (C) 2000 Wiley-Liss, Inc.