Effects of strychnine on the sodium conductance of the frog node of Ranvier.

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Abstract
The block of Na conductance was studied by reducing and slowing Na inactivation with scorpion venom. The block was voltage and time dependent. The more positive the axoplasm the greater the block and the faster the approach to equilibrium. Since evidence was presented suggesting that only open channels could be blocked. The block was reduced by raising internal Na or Li but not impermeant cations. A quaternary derivative of strychnine was synthesized and had the same action only when applied intracellularly. Strychnine blocked Na channels by a mechanism analogous to that by which it blocked K channels. The K channel block was identical to that by tetraethylammonium ion derivatives. Strychnine resembled procaine and its derivatives in its structure and the mechanism of Na channel block.