Influence of Na+ and Li+ ions on the kinetics of sodium channel block by tetrodotoxin and saxitoxin

Abstract

Voltage clamp experiments were done on single myelinated frog nerve fibres. The rate of block of Na+ channels by tetrodotoxin (TTX) was obtained from changes in peak Na+ current during 1-Hz trains of depolarizing impulses. In hypertonic Na(+)-rich solution (216 mM) the stationary block was reduced compared with Na(+)-poor solutions (54 mM or less; tetramethylammonium ions substituting for Na+). Washout in 216 mM Na+ was faster than in 54 mM Na+. Concentration of Na+ [( Na+]) little affected onset of block. After equilibration in Na(+)-poor TTX solution, a sudden application of Na(+)-rich toxin solution led to a partial relief from block that proceeded faster than the onset in the latter solution. Comparable results were obtained with saxitoxin (STX) and in analogous Li+ solutions. Most of the observed phenomena could be quantitatively fitted by a cyclic model in which cations favour the transition of channels (unblocked and blocked) from a high- to a low-affinity state from which toxin dissociates faster.

Assesment Criteria for Experimental Demyelination Induced in Frog Peripheral Nerve

“…Although intracellular recording of action potential is very adequate in terms of sensitivity, extracellular CAP analysis still maintains its importance from both experimental and clinical points of view (Hansen & Ulbricht, 1991;Lönnendonker et al, 1990;Poulter et al, 1993;Tan, 1985;Tan & Caliskan, 1988;Tan & Tan, 1995;Dalkilic & Pehlivan, 2002a).…”

Correlational Patch-Clamp Spectrometry of the Ion Channels

“…На данный момент имеются десятки статей по: замещающему действию ионов Rb + на калиевые каналы (см., напр. : [88][89][90][91][92][93][94][95][96][97][98][99][100][101][102] [154,[156][157][158][159][160][161][162][163][164][165] и др. металлов.…”