Changes in Infrared Spectrum of Nerve during Excitation

MOLECULAR changes that occur in the membrane of nerve during depolarization are important to explain the mechanism of excitation and conduction. During an action potential in nerve the electrical field strength across the membrane undergoes a change of about 10⁵ V cm^?1 which could influence the conformation of membrane molecules possessing a flexible dipole¹. Several methods have been reported for detecting changes with excitation in nerve, muscle and electroplaque^2–11, but have been difficult to interpret. We have therefore used an adaptation of the method of modulation spectroscopy¹², which is based on changes in the absorption spectrum as a result of perturbing the molecular structure^13–16. Our method was based on absorption in the infrared, which occurs for molecular vibrations accompanied by changes in dipole moment.