The action of hydrocarbons and carbon tetrachloride on the sodium current of the squid giant axon.

Abstract

The effects of the n-alkanes propane to hexane, cyclopropane, cyclopentane and cyclohexane and CCl4 on the ionic currents and electrical capacity of the squid giant axon membrane were examined. The peak inward and steady-state outward currents were reduced reversibly by each substance, although propane at 1 atm had little effect. The membrane capacity at 100 kHz was reduced by all substances except propane at 1 atm. Na currents were recorded in intracellularly perfused axons before and during exposure to the hydrocarbons and the records were fitted with equations similar to those proposed by Hodgkin and Huxley (1952). Shifts in the curves of the steady-state activation and inactivation parameters (m.infin. and k.infin.) against membrane potential, changes in the peak heights of the activation and inactivation time constants (.tau.m and .tau.n) and reductions in the maximum Na conductance (.hivin.gNa) were tabulated. The effects of the various hydrocarbons and CCl4 on the parameters of the Hodgkin-Huxley equations suggested that the suppression of the Na current by these substances originated from different phenomena. The underlying physicochemical events were considered in the light of the observed capacity changes and of information on artificial pore-containing membranes.