Modification of single Na+ channels by batrachotoxin.
The modifications in the properties of voltage-gated Na+ channels caused by batrachotoxin were studied by using the patch clamp method for measuring single channel currents from excised membranes of N1E-115 neuroblastoma cells. The toxin-modified open state of the Na+ channel has a decreased conductance in comparison to that of normal Na+ channels. The lifetime of the modified open state is drastically prolonged, and channels now continue to open during a maintained depolarization so that the probability of a channel being open becomes constant. Modified and normal open states of Na+ channels coexist in batrachotoxin-exposed membrane patches. Unlike the normal condition, Na+ channels exposed to batrachotoxin open spontaneously at large negative potentials. These spontaneous openings apparently cause the toxin-induced increase in Na+ permeability which, in turn, causes membrane depolarization.
D000818:Animals; D001496:Batrachotoxins / Q000494:pharmacology*; D002474:Cell-Free System; D002478:Cells, Cultured; D004553:Electric Conductivity; D007473:Ion Channels / Q000187:drug effects*; D007700:Kinetics; D008564:Membrane Potentials; D051379:Mice; D009447:Neuroblastoma
D001496:Batrachotoxins; D007473:Ion Channels