An artificial membrane-cable: decay and delay of electrical potentials along a lipid bilayer with ion channels

A model membrane is described which exhibits the properties of a neurite with respect to passive propagation of electrical potentials. A groove in a glass plate is covered by a black lipid membrane of glycerol monooleate. Gramicidin is incorporated. The stationary and transient response of the assembly is tested by two experiments: (i) One end of the groove is clamped at a constant voltage. The voltage at the other end and the total electrical current are measured. (ii) A charge pulse is injected at one end of the groove. The time-dependent voltage at the other end is measured. The results with respect to the lateral decay and delay of voltage are in quantitative agreement with the stationary and transient solutions of Kelvin's equation for a homogeneous cable. If gramicidin is incorporated unevenly along the membrane, the lateral decay of voltage is found to be asymmetric with respect to both directions. The cable is a partial one-way transmission line.