[The effect of aminobenzoic acid derivatives on the ion current of myelinated neurons. 2. Inactivation of sodium permeability].

Effects of Aminobenzoic Acid Derivatives on the Ionic Currents in Myelinated Nerve/2nd Communication: Sodium inactivation. Derivatives of aminobenzoic acid similar to metacaine were modified and their effects on the sodium inactivation and on the sodium permeability constant, PNa, of single potential clamped myelinated nerve fibres were tested. Comparing the observed shift of the inactivation curves and the reduction of PNa with the octanol/water partition coefficients of the drugs tested, a minimum lipid solubility seems to be necessary for the substances being efficacious. It is assumed that the uncharged aminobenzoic acids reduce PNa by disturbing the lipid matrix in an unspecific manner. The observed shift of the inactivation curves is explained in terms of the fixed charges at the inside of the membrane being moved apart by the uncharged compounds thus lowering the effective membrane potential. Moreover, no indications for a receptor-mediated mechanism were found.