Block of sodium conductance by n-octanol in crayfish giant axons

The block of the Na+ current by n-octanol was studied in crayfish giant axons under axial wire voltage-clamp conditions. Standard kinetic analysis of the Na+ currents was undertaken to test the hypothesis tha the n-octanol-induced block of the Na+ current could be accounted for on the basis of changes in the voltage dependence of the kinetic parameters. Alterations in the membrane dipolar potential arising from rearrangement of membrane lipids would be the anticipated source of changes in the voltage dependence. Although some changes in voltage dependence did evolve with the block by n-octanol, the changes were not of sufficient magnitude to account for the block. In conclusion, although higher concentrations of n-octanol produced shifts along the voltage axis of the kinetic parameters, direct blocking action of n-octanol on the channel appears to be the most important mechanism of the block.