Ion channel that contributes to passive transmembrane potassium transport and to the regulation of the resting membrane potential in brain astrocytes, but also in kidney and in other tissues. Forms dimeric channels through which potassium ions pass in accordance with their electrochemical gradient. The channel is selective for K+ ions at physiological potassium concentrations and at neutral pH, but becomes permeable to Na+ at subphysiological K+ levels and upon acidification of the extracellular medium. Channel activity is modulated by activation of serotonin receptors. Heterodimeric channels containing KCNK1 and KCNK2 have much higher activity, and may represent the predominant form in astrocytes. Heterodimeric channels containing KCNK1 and KCNK3 or KCNK9 have much higher activity. Heterodimeric channels formed by KCNK1 and KCNK9 may contribute to halothane-sensitive currents. Mediates outward rectifying potassium currents in dentate gyrus granule cells and contributes to the regulation of their resting membrane potential. Contributes to the regulation of action potential firing in dentate gyrus granule cells and down-regulates their intrinsic excitability. In astrocytes, the heterodimer formed by KCNK1 and KCNK2 is required for rapid glutamate release in response to activation of G-protein coupled receptors, such as F2R and CNR1.