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Two Types of Potassium Current in Rabbit Cultured Schwann Cells

J. R. Howe and J. M. Ritchie
Proceedings of the Royal Society of London. Series B, Biological Sciences
Vol. 235, No. 1278 (Oct. 22, 1988), pp. 19-27
Published by: Royal Society
Stable URL: http://www.jstor.org/stable/36235
Page Count: 9
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Two Types of Potassium Current in Rabbit Cultured Schwann Cells
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Abstract

Voltage-gated outward currents were studied in rabbit cultured Schwann cells with the `whole-cell' configuration of the patch-clamp method. Four components of such currents were identified. The first, which was abolished by replacement of the external chloride ions by the large impermeant anion gluconate, was identified as a chloride current. The second and third were identified as potassium currents. One type of potassium current was reduced substantially by either 4-aminopyridine (4-AP) or tetraethylammonium ion (TEA). Its sensitivity to blocking by 4-AP was highly voltage-dependent: the equilibrium dissociation constant (K) was threefold greater when measured at +10 mV than when measured at -40 mV (where it was about 80 μ M). The second type of potassium current was relatively insensitive to 4-AP, but was blocked by TEA. The TEA sensitivity of the two types of potassium currents was similar and displayed no obvious voltage-dependence (K ≈ 200 μ M). The fourth component of current was not reduced by 4-AP or TEA at concentrations less than 10 mM. Whether or not this last component is a potassium current is unclear.

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