Transient fluorescence signals from pyrene labeled pike nerves during action potential possible implications for membrane fluidity changes

Pike olfactory nerves labeled with pyrene and illuminated at 340 nm showed a highly resolved monomer fluorescence emission and a broad excimer emission band at longer wavelength. The excimer formation being controlled by lateral diffusion in the membrane lipids, the ratio of both maxima emission amplitudes is a fluidity parameter and was found to depend on temperature. When these nerves were stimulated, this ratio (F) underwent a small transient decrease ($\text{Δ}\text{F}\text{F}$ range = 10^?3 to 10^?4), synchronous with the propagated impulse. These findings may be interpreted as a transient decreased fluidity of the membrane lipids during excitation