Analgesic Effects of the Polarized Red+Infrared LED Light

Abstract

INTRODUCTION: Our previous studies have shown that exposure of acupuncture points (AP) or painful area of mice to halogen polarized light (PL) effectively weakens the pain. The aim of the study was to determine whether exposure of AP or painful area to LED red-infrared PL evokes analgesic effect. METHODS: The duration of licking the formalin-injected foot (tonic pain) was recorded in control group and mice exposed (5 min, 10 min) to red+infrared LED light on AP E-36 or on the painful area. Power density of the light varied from 0.3 to 16.5 mW/cm 2 . RESULTS: Exposure of AP E-36 or painful area to red-infrared LED PL evoked statistically significant decrease of licking time. The effect depended on the light application duration and its power density. 10-minute light exposition was more effective than 5-minute. The exposure of pain source to LED PL shortened the licking time to 44.1% (at 16.5 mW/cm 2 ) and to 64.4% (at 0.3 mW/cm 2 ). CONCLUSION: The results show the efficacy of pain suppression by exposure of antinociceptive AP or painful area to LED red+infrared PL. The effect depends on the duration of light exposure and its power density.