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
