The mechanism of anaesthesia: a new hypothesis based on the effects on electrical properties of a model membrane: preliminary studies.

Changes induced by inhalational anaesthetic agents were investigated in a simple membrane model. All the agents tested increased the membrane's electrical capacitance and conductance linearly, proportional to concentration and potency, and decreased its dialectric strength independently of concentration. When protein was substituted for lipid, the same agents had no significant effect on capacitance, conductance, or dielectric strength. Based on these findings, the following hypothesis is presented. Anaesthetic agents exert their influence on the lipid portion of nerve membranes. They enhance excitability by reducing the dielectric strength of the membrane and depress excitability by increasing the membrane's dielectric constant and passive conductance. The degree of excitability or narcosis at any instant depends upon the relative magnitude of these opposing effects.