Effect of Anesthetics on Action Potential Propagation

Abstract

Local anesthesia has been attributed to the specific interaction of local anesthetics with (sodium) channel proteins, while the action of general anesthetics still remains unclear. However, already at the beginning of 20th century Meyer and Overton independently found that the critical anesthetic dose of anesthetics, regardless of their types, is linearly proportional to their solubility in olive oil. Based on this finding, in 2005 Heimburg and Jackson proposed that the action potential is a density pulse (soliton) propagating in biological membranes, which explains anesthesia by freezing point depression law that originates from van’t Hoff's law. In this work, we conduct experiments on nerves from lobsters and earthworms to study the effect of anesthetics on compound action potential and action potential from a single neuron. The experimental data are then compared with the simulation results by solving the soliton equations in 1D cylindrical membrane with anesthetics inside the system. Anesthetics move the chain melting transition temperature of membranes far away from the physiological temperature, which requires a higher free energy to induce the phase transition, resulting in a higher stimulation voltage to reach the maximum amplitude of the action potential.