Basic research for Ar laser in the spinal cord

The cat's spinal dorsal column was irradiated with Ar of which power output was 500 mW and the spot size was 2mm in diameter. The somatosensory evoked potential was recorded. The conclusion can be summerized as follows;(1) When the smaal demarcated area was made in the surface of the dorsal column with Ar laser irradiation, the early component of S. E. P. was disappeared. The histological examination shows the irradiated dorsal column was destroyed almost overall.(2) By using the photosensitizing dye fluorescein i. v., the photoactivation effect of Ar laser was demonstrated in the spinal cord. The S. E. P. change and histological findings were the same as those of the experiment without using dye. So for evaluation of the photosensitizing agent in the spinal cord, the S. E. P. can be taken as the monitor of the Laser-Photo-Biological-Effect (L. P. B. h.).