Abstract
Strychnine blocks sodium conductance in the frog node of Ranvier. This block was studied by reducing and slowing sodium inactivation with scorpion venom. The block is voltage and time dependent. The more positive the axoplasm the greater the block and the faster the approach to equilibrium. Some evidence is presented suggesting that only open channels can be blocked. The block is reduced by raising external sodium or lithium but not impermeant cations. A quaternary derivative of strychnine was synthesized and found to have the same action only when applied intracellularly. We conclude that strychnine blocks sodium channels by a mechanism analogous to that by which it blocks potassium channels. The potassium channel block had previously been found to be identical to that by tetraethylammonium ion derivatives. In addition, strychnine resembles procaine and its derivatives in both its structure and the mechanism of sodium channel block.
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Selected References
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- Armstrong C. M. Inactivation of the potassium conductance and related phenomena caused by quaternary ammonium ion injection in squid axons. J Gen Physiol. 1969 Nov;54(5):553–575. doi: 10.1085/jgp.54.5.553. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Armstrong C. M. Interaction of tetraethylammonium ion derivatives with the potassium channels of giant axons. J Gen Physiol. 1971 Oct;58(4):413–437. doi: 10.1085/jgp.58.4.413. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Cahalan M. D. Modification of sodium channel gating in frog myelinated nerve fibres by Centruroides sculpturatus scorpion venom. J Physiol. 1975 Jan;244(2):511–534. doi: 10.1113/jphysiol.1975.sp010810. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Courtney K. R. Mechanism of frequency-dependent inhibition of sodium currents in frog myelinated nerve by the lidocaine derivative GEA. J Pharmacol Exp Ther. 1975 Nov;195(2):225–236. [PubMed] [Google Scholar]
- Hille B. Ionic selectivity, saturation, and block in sodium channels. A four-barrier model. J Gen Physiol. 1975 Nov;66(5):535–560. doi: 10.1085/jgp.66.5.535. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hille B. The permeability of the sodium channel to metal cations in myelinated nerve. J Gen Physiol. 1972 Jun;59(6):637–658. doi: 10.1085/jgp.59.6.637. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shapiro B. I. Effects of strychnine on the potassium conductance of the frog node of Ranvier. J Gen Physiol. 1977 Jun;69(6):897–914. doi: 10.1085/jgp.69.6.897. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shapiro B. I., Wang C. M., Narahashi T. Effects of strychnine on ionic conductances of squid axon membrane. J Pharmacol Exp Ther. 1974 Jan;188(1):66–76. [PubMed] [Google Scholar]
- Strichartz G. R. The inhibition of sodium currents in myelinated nerve by quaternary derivatives of lidocaine. J Gen Physiol. 1973 Jul;62(1):37–57. doi: 10.1085/jgp.62.1.37. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tritthart H., Fleckenstein B., Fleckenstein A. Some fundamental actions of antiarrhythmic drugs on the excitability and the contractility of singel myocardial fibers. Naunyn Schmiedebergs Arch Pharmakol. 1971;269(2):212–219. doi: 10.1007/BF01003038. [DOI] [PubMed] [Google Scholar]
- Woodhull A. M. Ionic blockage of sodium channels in nerve. J Gen Physiol. 1973 Jun;61(6):687–708. doi: 10.1085/jgp.61.6.687. [DOI] [PMC free article] [PubMed] [Google Scholar]