Proton modulation of outward K+ currents in interferon-gamma-activated microglia.

Whole-cell outward potassium currents (IK) were measured in interferon (IFN)-gamma-activated cultured murine microglial cells. Acidification of the external milieu moved the threshold of activation of IK in a depolarizing direction, while alkalinization showed the opposite effect. A shift of more than 20 mV of the steady-state activation and inactivation curves of IK in hyperpolarizing direction was measured when pH was changed from 5.8 to 7.8. The time-dependent inactivation of IK was slower when superfusing cells with acid solutions than with alkaline ones. In contrast, variations in the pH of the intracellular solution did not alter kinetics of IK. However, alkalinization of the internal solution from a pH of 5.8 to 7.8 led to a two-fold increase in the current density of IK.