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. 1986 Mar;49(3):629-43.
doi: 10.1016/S0006-3495(86)83690-6.

Saxitoxin and tetrodotoxin. Electrostatic effects on sodium channel gating current in crayfish axons

S T Heggeness, J G Starkus

Saxitoxin and tetrodotoxin. Electrostatic effects on sodium channel gating current in crayfish axons

S T Heggeness et al. Biophys J. 1986 Mar.

Abstract

The effects of extracellular saxitoxin (STX) and tetrodotoxin (TTX) on gating current (IgON) were studied in voltage clamped crayfish giant axons. At a holding potential (VH) of -90 mV, integrated gating charge (QON) was found to be 56% suppressed when 200 nM STX was added to the external solution, and 75% suppressed following the addition of 200 nM TTX. These concentrations of toxin are sufficiently high to block greater than 99% of sodium channels. A smaller suppression of IgON was observed when 1 nM STX was used (KD = 1-2 nM STX). The suppression of IgON by external toxin was found to be hold potential dependent, with only minimal suppression observed at the most hyperpolarized hold potentials, -140 to -120 mV. The maximal effect of these toxins on IgON was observed at hold potentials where the QON vs. VH plot was found to be steepest, -100 to -80 mV. The suppression of IgON induced by TTX is partially relieved following the removal of fast inactivation by intracellular treatment with N-bromoacetamide (NBA). The effect of STX and TTX on IgON is equivalent to a hyperpolarizing shift in the steady state inactivation curve, with 200 nM STX and 200 nM TTX inducing shifts of 4.9 +/- 1.7 mV and 10.0 +/- 2.1 mV, respectively. Our results are consistent with a model where the binding of toxin displaces a divalent cation from a negatively charged site near the external opening of the sodium channel, thereby producing a voltage offset sensed by the channel gating apparatus.

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References

    1. J Membr Biol. 1978 Jan 18;38(3):271-89 - PubMed
    1. J Gen Physiol. 1975 Jul;66(1):47-65 - PubMed
    1. Biophys J. 1983 Mar;41(3):269-74 - PubMed
    1. J Physiol. 1975 Jul;248(3):613-24 - PubMed
    1. J Gen Physiol. 1969 Nov;54(5):589-606 - PubMed

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