Bioelectric changes in single neuron under photodynamic effect: comparison of different photosensitizers

An isolated crayfish mechanoreceptor neuron was used as a new test object for a cytophysiological study of various photosensitizers (methylene blue, janus green B, protoporphyrin IX, chlorins e6 and p6). The study of single neuron response provides evaluation of the dynamics of cytotoxic events leading from initial threshold changes to cell death. The typical response of a photosensitized neuron to He-Ne laser irradiation was firing acceleration and then irreversible block of spike generation. Crayfish neurons were very sensitive to the photodynamic effect; they changed firing rate and died at nanomolar concentrations of photosensitizers. Dependencies of spike acceleration rate and neuron lifetime on photosensitizer concentration allowed one to compare efficiencies of different photosensitizers. Chlorin p6, chlorin e6, and methylene blue were the most potent photosensitizers.