Voltage-dependent sodium and potassium channels in mammalian cultured Schwann cells.
Cultured Schwann cells from sciatic nerves of newborn rabbits and rats have been examined with patch-clamp 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.
Shrager
P
P
Chiu
S Y
SY
Ritchie
J M
JM
D000818:Animals; D002478:Cells, Cultured; D004558:Electric Stimulation; D004594:Electrophysiology; D007473:Ion Channels / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits; D011901:Ranvier's Nodes / Q000502:physiology; D051381:Rats; D012530:Saxitoxin / Q000378:metabolism; D012583:Schwann Cells / Q000502:physiology*; D012584:Sciatic Nerve / Q000166:cytology; D012964:Sodium / Q000378:metabolism*
D007473:Ion Channels; D012530:Saxitoxin; D012964:Sodium; D011188:Potassium