Voltage-dependent tetrodotoxin binding to single batrachotoxin-modified Na channels recorded from intact neuroblastoma cells.
To clarify the voltage-dependent actions of tetrodotoxin (TTX) on Na channels in cellular membranes, we examined the TTX block of single batrachotoxin-modified Na channels in neuroblastoma cells. We found these Na channels had a high affinity for TTX which decreased e-fold per 35.5 mV depolarization. The decrease in affinity resulted primarily from a decrease in the blocking rate for TTX; the unblocking rate increased slightly with depolarization. While the voltage-dependence of TTX binding to neuroblastoma Na channels was similar to that reported in purified Na channels incorporated in bilayers, the magnitude and voltage-dependence of the rate constants were quite different.
McPherson
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DR
Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77550.
Huang
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LY
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001496:Batrachotoxins / Q000494:pharmacology*; D004566:Electrodes; D008051:Lipid Bilayers / Q000737:chemistry; D051379:Mice; D009447:Neuroblastoma / Q000378:metabolism*; D012530:Saxitoxin / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*; D013779:Tetrodotoxin / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
D001496:Batrachotoxins; D008051:Lipid Bilayers; D015222:Sodium Channels; D012530:Saxitoxin; D013779:Tetrodotoxin