Properties of the leakage current pathway: effects of the gadolinium ion on myelinated axons.

Voltage-clamp experiments on myelinated axons revealed that the trivalent gadoliniumion ion blocked the leakage current in a dose-dependent manner. The block showed 1:2 stoichiometry, and 50% reduction at 700 microM. Na+ and K+ currents were blocked at ten times lower concentration and showed 1:1 stoichiometry. Comparisons with biochemical studies suggest that the leakage current directly depends on a phospholipid pathway in contrast to the protein-channel dependent Na+ and K+ currents. The results may be explained by a leakage current pathway located at the interface between channel proteins and the lipid phase.