Figure 3.

High potassium permeability of glial cells is mediated by K_ir4.1 channels. (A) Schematic illustration of simultaneous recordings of extracellular K⁺ concentration (K⁺) and glial membrane potential (INTRA). (B) In vivo simultaneous recordings of extracellular K⁺ concentrations and glial membrane potential fluctuations during long lasting stimulations (10 Hz, 30 s). Glial membranes behave as K⁺ electrodes, reflecting their high K⁺ permeability. Abbreviation for Nernst equation: R, universal gas constant; T, temperature; F, Faraday constant; E_K, K⁺ equilibrium potential; Vm, membrane potential; [K⁺]_o, extracellular K⁺ concentration; [K⁺]_i, intracellular K⁺ concentration. (C) Similar protocol applied in a K_ir4.1 knockout animal. Glial membrane potential does not follow K⁺ fluctuations, indicating a strong loss of K⁺ conductances. A small and delayed depolarization, which is not associated with K⁺ increase, could, however, be observed in response to long lasting stimulations only. Adapted, with permission, from Chever et al. (2010) (B,C).