Changes in fluorescence, turbidity, and birefringence associated with nerve excitation.

Abstract

The objective of this paper is to offer experimental evidence which shows that the process of excitation in the nerve is accompanied by a transient change in optical properties of the nervous tissue. The optical properties examined include fluorescence, turbidity, and birefringence.Changes in fluorescence were examined after nervous tissues were stained with the dye 8-anilinonaphthalene-1-sulfonic acid (ANS).1 Our search for fluorescence under these conditions was prompted by the work of Aronson, Detert, and Morales,2 who demonstrated that the fluorescence of ANS is extremely sensitive to conformational changes of various macromolecules.Our attempt to measure turbidity changes of the nerve during excitation was made with a view to extending the work reported by Cohen and Keynes3 by the use of monochromatic light.The observation by Inoue and Sato4 of rapid changes in the mitotic figure of the Pectinaria obcyte under a polarizing microscope aroused our interest in the birefringent properties of the nerve during excitation. Our experiments along this line were greatly accelerated when we encountered a very significant paper by Cohen et al.5 on this subject in the early stages of our investigation.Changes in the optical properties of the nerve during excitation are very small. In fluorescence and turbidity studies, optical signs of nerve excitation could not be measured without the use of a computer to average multiple responses. However, in birefringence studies, it was possible to record optical signs of nerve excitation directly on an oscillograph screen.

On soliton propagation in biomembranes and nerves

“…It is not a thermodynamic theory, and its language contains neither temperature and pressure nor entropy, heat, or volume. Various authors have noted that the action potential is accompanied by reversible mechanical dislocations, changes in volume and temperature (11-16, 27, 32), and changes in fluorescence, turbidity, and birefringence (17). In particular, data indicate that heat release is exactly in phase with the action potential (12,13), and that there is no net heat release after completion of the action potential.…”

“…In fact, mechanical forces and dislocations as well as temperature responses of nerve membranes in-phase with the action potential have been found experimentally (11)(12)(13)(14)(15)(16). They are accompanied by changes in the fluorescence of membrane probes and changes in turbidity and birefringence (17). None of these phenomena play a role in the Hodgkin-Huxley theory (18) that is the accepted model of nerve pulses.…”

Imaging membrane potential in dendrites and axons of single neurons

“…The first optical recordings of fast membrane potential changes, however, were not performed until the late 1960s, in experiments that detected changes in light scattering and birefringence, as well as fluorescence, during single action potentials in crab, lobster, and squid axons [11,53]. It was subsequently discovered that by staining preparations with "merocyanine" dyes, the signal-to-noise ratio of measurements of membrane potential could be significantly increased [13].…”

Mechanical, thermal, and optical changes of the nerve membrane associated with excitation.

“…With the use of proper dyes, the wavelength of this "extrinsic fluorescence" can be brought into the region of the visible light, which is more easily measured than the ultraviolet emission. The extrinsic fluorescence signal was first detected by TASAKI et al [68]. The usefulness of the signal was greatly increased when DAVILA et al [27] found that merocyanine dye gives an extraordinarily large fluorescence signal from the squid giant axon.…”