Kinetics of potassium movement in norman cortex

Artificial CSF containing 12mEq/1 of potassium (4 times normal concentration) was perfused over the surface of normal neocortex in 10 locally or barbiturate anesthetized cats. Extracellular potassium concentrations ([K+]OS) were measured as a function of time to 8 h and of depth to 3 mm. Analysis of the [K+]O versus depth and [K+]O versus time profiles showed that the distribution of extracellular potassium could be modelled by a process of diffusion with diffusion coefficient = 1.03 +/- 0.16 sq.mm/h, and a surface barrier to diffusion with magnitude given by a barrier constant 0.8 +/- 0.2 mm-1, and with a small correction for active uptake into cells and blood vessels. The profiles obtained differ considerably from those which could be predicted from kinetic properties of potassium in aqueous solution.