Abstract
Voltage-gated whole-cell currents were recorded from cultured microglial cells which had been developed in the presence of the macrophage/microglial growth factor granulocyte/macrophage colony-stimulating factor. Outward K+ currents (I K) were most prominent in these cells. I Kcould be activated at potentials more positive than −40 mV. Half-maximal activation of I Kwas achieved at −13.8 mV and half-maximal inactivation of I Kwas determined at −33.8 mV. The recovery of I Kfrom inactivation was described by a time constant of 7.9 sec. For a tenfold change in extracellular K+ concentration the reversal potential of I Kshifted by 54 mV.
Extracellularly applied 10 mm tetraethylammonium chloride reduced I K by about 50%, while 5 mm 4-aminopyridine almost completely abolished I K. Several divalent cations (Ba2+, Cd2+, Co2+, Zn2+) reduced current amplitudes and shifted the activation curve of I Kto more positive values. Charybdotoxin (IC50 = 1.14 nm) and noxiustoxin (IC50=0.89 nm) blocked I Kin a concentration-dependent manner, whereas dendrotoxin and mast cell degranulating peptide had no effect on the current amplitudes.
The outward K+ currents showed a frequency dependence when depolarizing pulses were applied at a frequency of 1 Hz. A frequency-independent outward current (I K′) characterized by the same activation behavior as I Kwas detected. I K′was blocked completely by 10 nm charybdotoxin or by 10 nm noxiustoxin. In contrast to its effect on I K, 10 mm tetraethylammonium chloride did not reduce I K′.
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The authors wish to thank B. Nitzgen for the preparation of cell cultures, M. Bullmann for technical assistance and F. Dreyer for helpful discussions and critical reading of the manuscript. We are grateful to F. Seiler, F. Dreyer and L. Possani for the generous gifts of r GM-CSF, dendrotoxin and noxiustoxin. This work was supported by DFG grant He-1128/6-2 and SFB 194 projects B3 and B11.
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Eder, C., Fischer, H.G., Hadding, U. et al. Properties of voltage-gated potassium currents of microglia differentiated with granulocyte/macrophage colony-stimulating factor. J. Membarin Biol. 147, 137–146 (1995). https://doi.org/10.1007/BF00233542
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DOI: https://doi.org/10.1007/BF00233542