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  • 1
    Electronic Resource
    Electronic Resource
    Pharmacological properties of Ca2+-activated K+ currents of ramified murine brain macrophages (1997)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 356 (1997), S. 233-239 
    Details
    ISSN: 1432-1912
    Keywords: Key words Brain macrophages ; Mice ; Ca2+-activated K+ currents ; Patch clamp ; Whole-cell recording ; Peptide toxins ; Polyvalent cations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using the whole-cell configuration of the patch clamp technique, calcium-activated potassium currents (IK,Ca) were investigated in ramified murine brain macrophages. In order to induce IK,Ca the intracellular concentration of nominal free Ca2+ was adjusted to 1μM. The Ca2+-activated K+ current of brain macrophages did not show any voltage dependence at test potentials between –120 and +30mV. A tenfold change in extracellular K+ concentration shifted the reversal potential of IK,Ca by 51mV. The bee venom toxin apamin applied at concentrations of up to 1μM did not affect IK,Ca. Ca2+-activated K+ currents of ramified brain macrophages were highly sensitive to extracellularly applied charybdotoxin (CTX). The half-maximal effective concentration of CTX was calculated to be 4.3nM. In contrast to CTX, the scorpion toxin kaliotoxin did not inhibit IK,Ca at concentrations between 1 and 50nM. Tetraethylammonium (TEA) blocked 8.0% of IK,Ca at a concentration of 1mM, whereas 31.4% of current was blocked by 10mM TEA. Several inorganic polyvalent cations were tested at a concentration of 2mM for their ability to block IK,Ca. La3+ reduced IK,Ca by 72.8%, whereas Cd2+ decreased IK,Ca by 17.4%; in contrast, Ni2+ did not have any effect on IK,Ca. Ba2+ applied at a concentration of 1mM reduced IK,Ca voltage-dependently at hyperpolarizing potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005046
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Properties of voltage-gated potassium currents of microglia differentiated with granulocyte/macrophage colony-stimulating factor (1995)
    Springer
    The journal of membrane biology 147 (1995), S. 137-146 
    Details
    ISSN: 1432-1424
    Keywords: Microglia ; Granulocyte/macrophage colony-stimulating factor ; Whole-cell recording ; Outward K+ currents ; Frequency-independent K+ current ; Peptide toxins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: 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′.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233542
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    Paper (German National Licenses)
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