Effect of photosensitization reaction on myelinated or unmyelinated nerve

To investigate nerve injury by a photosensitization reaction ex vivo, we observed an uptake of talaporfin sodium into crayfish nerve and porcine phrenic nerve, and measured electrophysiological conduction velocity of the crayfish nerve during the reaction. We found the drug uptake of inside the perineurium was lower than that of outside in porcine phrenic nerve. The crayfish nerve was immersed into 20 µg/ml talaporfin sodium for 15 min and irradiated by a 663 nm laser light with 120 mW/cm². Since we found the measured conduction velocity was decreased increasing the irradiation time, the nerve might not be resistant to the photosensitization reaction at atmospheric oxygen environment. It was reported that the phrenic nerve was intact when an electro blockade using photosensitization reaction was performed in vivo animal experiment. Low uptake of talaporfin sodium inside the perineurium and low oxygen partial pressure of nerve might be the mechanism to preserve phrenic nerve in vivo animal experiment.