Of the patients with sciatica, osteoarthritis and others, 116 of 149 experienced pain relief with the low power laser irradiation (LPLI). To investigate the neuronal mechanism of the effects of LPLI, we analyzed the effects of LPLI upon neuronal activities of sensory nerve by neurophysiological studies. LPLI upon sensory nerve suppressed flexion reflex afferent induced cord dorsum potential as well as sensory nerve discharge evoked by noxious stimulation. These results suggested that the analgesic effects of LPLI might be caused by blockade of conduction in the sensory nerve.
