Voltage-gated potassium currents in myelinating Schwann cells in the mouse
Abstract
1. The whole-cell variation of the patch-clamp technique was used to record ionic currents in Schwann cells obtained from enzyme-treated mouse sciatic nerves before and after the onset of myelination. 2. Only outward currents were evoked in embryonic Schwann cells, which had no myelin, at membrane potentials more positive than -40 mV. Neonatal myelinating cells developed depolarization-activated outward currents and hyperpolarization-activated inward currents. For large hyperpolarizations below -160 mV, inward currents exhibited a sag following a peak which appeared to be mainly due to Na+ blockade. 3. Membrane potentials of neonatal myelinating cells were more negative than those of embryonic cells. The depolarization of the membrane potentials per 10-fold increase in external K+ concentrations in neonatal myelinating cells was 57 mV which fits the Nernst equation for a K+ electrode. 4. Quinine (0.5-2 mM) blocked the outward currents in embryonic cells and Ba2+ (2 mM) blocked both outward and inward currents in neonatal myelinating cells leaving quinine-sensitive outward currents of the embryonic type. External Cs+ (5 mM) blocked mainly inward currents and internal Cs+ blocked outward currents. 5. Developmental changes of thes...Continue Reading
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