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

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Abstract
The K block was voltage-dependent and reached a steady level with a relaxation time of 1 to several ms. Block was increased by depolarization or a reduction in [K+]o as well as by increasing strychnine concentration. A quaternary derivative of strychnine produced a similar block only when applied intracellularly. Strychnine block resembled that produced by intracellular application of the substituted tetraethylammonium compounds. The kinetics, voltage dependence and dependence on [K+]o of strychnine block were of the same form. Tertiary strychnine must cross the axon membrane and block from the axoplasmic side in the same fashion as these quaternary amines.