Changes in proton currents in murine microglia induced by cytoskeletal disruptive agents

Voltage-gated proton currents (I PR) were investigated in cultured murine microglia using the whole-cell configuration of the patch clamp technique. At a gradient of 1.5 between intracellular (pH i=6.0) and extracellular pH (pH o=7.5) values, outward I PR were detected at depolarizing potentials, while the activation threshold of I PR was −40 mV. Time-dependent activation of I PR was fitted by a single exponential with a time constant of 661 ms at +40 mV. An increase in the activation time constant of I PR was seen after exposure of microglia to the cytoskeletal disruptive agents cytochalasin D or colchicine. Moreover, the current density of I PR was significantly reduced by 49% in cells treated with cytochalasin D and by 27% in cells treated with colchicine for 24 h. In contrast, voltage-dependence of steady-state activation of I PR was unchanged after disruption of the cytoskeleton. Exposure of microglia to the cytoskeletal stabilizers phalloidin and taxol did not affect I PR of microglia.