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Voltage-Dependent Sodium and Potassium Channels in Mammalian Cultured Schwann Cells
P. Shrager, S. Y. Chiu and J. M. Ritchie
Proceedings of the National Academy of Sciences of the United States of America
Vol. 82, No. 3 (Feb. 1, 1985), pp. 948-952
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25390
Page Count: 5
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Cultured Schwann cells from sciatic nerves of newborn rabbits and rats have been examined with patchclamp techniques. In rabbit cells, single sodium and potassium channels have been detected with single channel conductances of 20 pS and 19 pS, respectively. Single sodium channels have a reversal potential within 15 mV of ENa, are blocked by tetrodotoxin, and have rapid and voltage-independent inactivation kinetics. Single potassium channels show current reversal close to EK and are blocked by 4-aminopyridine. From these results, and from comparisons of single-channel and whole-cell data, we show that these Schwann cells contain voltage-dependent sodium and potassium channels that are similar in most respects to the corresponding channels in mammalian axonal membranes. Cultured rat Schwann cells also have sodium channels, but at a density about 1/10th that of rabbit cells, a result in agreement with saxitoxin binding experiments on axon-free sectioned nerves. Saxitoxin binding to cultured cells suggests that there are up to 25,000 sodium channels in a single rabbit Schwann cell. We speculate that in vivo Schwann cells in myelinated axons might act as a local source for sodium channels at the nodal axolemma.
Proceedings of the National Academy of Sciences of the United States of America © 1985 National Academy of Sciences