The action of salicylate ions on the frog node of Ranvier.

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Abstract
The effects of salicylate on the membrane currents in the frog node of Ranvier were studied. External salicylate slows the falling phase of the action potential and with little effect on the action potential and with little effect on the action potential amplitude. External salicylate has no effect on the leak current. Most of the actions of external salicylate are due to a simple incorporation of negative charges into the membrane surface. The h.infin., .tau.h [time constant for the Na current h gating system], .tau.m [time constant for the Na current m gating system] and m.infin. [test pulse potential for the Na current m gating system] curves for the Na current are shifted to more negative potentials, as are the n.infin. [test potential for the K current n gating system] and k.infin. [test potential for the slow K inactivation current] curves for the K current. K ion accumulation prevented analysis of the action of salicylate on the time constant of K current kinetics. In addition to the h.infin. and .tau.h curves being shifted to more negative potentials, the shapes of the curves are changed by salicylate. These shape changes cannot be explained by conventional homogeneous surface charge theory. Explanations for the changes are discussed. Internal salicylate has similar effects to external salicylate: the gating variable curves for the Na current are shifted in the negative direction on the voltage axis, rather than in the positive direction expected if negative charges were added to the innersurface of the nodal membrane. This may be due to salicylate crossing the membrane and binding preferentially to a receptor at the external surface, or might be due to a rise in intracellular Ca concentration after inhibition of oxidative phosphorylation.