Bioelectric response of single neuron to photodynamic action of chlorin e6

Photodynamic effect of chlorin e6 on bioelectric activity of single crayfish stretch receptor neuron was studied. The stable background firing of this cell provides precise evaluation of initial membrane activity shifts, dynamics of bioelectric changes, and terminal events leading to the cell death. Spikes of isolated neuron were amplified, and their frequency was continuously recorded. After 1 hour of stable control work neurons were incubated 30 min in saline with various chlorin e6 concentrations from 30 to 500 nM, and then irradiated by helium-neon laser(632.8 nm, 0.3 W/cm). Irradiation increased firing frequency and then induced abrupt irreversible cessation of spike generation. Rate of firing acceleration and neuron lifetime quadratically depended on the dye concentration, hence the excitation of two dye molecules is need for neuron response. These data show that bioelectric activity of single nerve cell is very sensitive to chlorin e6 photodynamic injury and that plasma membrane is the main target of photodynamic effect.