Properties of voltage-gated currents of microglia developed using macrophage colony-stimulating factor.
Microglia were isolated from a murine neonatal brain cell culture in which their development had been stimulated by supplementation with the macrophage/microglial growth factor macrophage colony-stimulating factor (M-CSF). Using the whole-cell configuration of the patch-clamp technique, voltage-gated membrane currents were recorded from these microglial cells. Hyperpolarization induced inward rectifying K+ currents, as described for microglia from untreated cultures. These currents activated negative to the K+ equilibrium potential and, with a strong hyperpolarization, displayed time-dependent inactivation. The inactivation was abolished when extracellular NaCl was replaced by N-methyl-D-glucamine (NMG), thereby indicating a partial block of this K+ conductance by Na+. Inward rectifying currents were also blocked by extracellularly applied Cs+ or Ba2+. They were slightly diminished following treatment with extracellular tetraethylammonium chloride (TEA) but were not affected by 4-aminopyridine (4-AP). Upon long lasting depolarizing voltage pulses to potentials positive to 0 mV, the cells exhibited a slowly activating H+ current which could be reduced by application of inorganic polyvalent cations (Ba2+, Cd2+, Co2+, La3+, Ni2+, Zn2+) as well as by 4-AP or TEA. Based on their kinetics and pharmacological characteristics, both currents detected on M-CSF-grown microglia are suggested to correspond to the inward rectifier and the H+ current of macrophages.
D000818:Animals; D000831:Animals, Newborn; D001464:Barium / Q000378:metabolism; D002412:Cations / Q000378:metabolism; D002478:Cells, Cultured; D004594:Electrophysiology; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D016173:Macrophage Colony-Stimulating Factor / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008809:Mice, Inbred C3H; D017628:Microglia / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000502:physiology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D002412:Cations; D007473:Ion Channels; D013757:Tetraethylammonium Compounds; D001464:Barium; D016173:Macrophage Colony-Stimulating Factor; D011188:Potassium