Lizarelli RFZ*, Paolillo FR, Jorge AES, Regalo SCH, Parizotto NA and Bagnato VS
Purpose: Searching for effective doses and wavelengths, this study evaluated the effects of LED (light emitting diode) and LASER on induced abdominal pain in male mice. Methods: Forty-nine male mice were divided into 7 groups: G1 – control untreated; G2 – infrared laser 37.5 J/cm2; G3 – infrared laser 75 J/cm2; G4 – infrared LED 37.5 J/cm2; G5 – infrared LED 75 J/cm2; G6 – red LED 37.5 J/cm2; G7 – red LED 75 J/cm2. Intraperitoneal injection of 0.15 mL of 1 % acetic acid solution was used to induce pain and abdominal writhings. Immediately after the injection, except for G1 group, the animals were treated with Laser (808 nm, continuous mode, irradiation time of 20 seconds, fluency of 37.5 and 75 J/cm2, average power of 70 mW and 150 mW respectively, according to the groups) and LED (850 ± 5 nm or 630 ± 5 nm, continuous mode, irradiation time of 20 seconds, fluency of 37.5 and 75 J/cm2, average power of 70 mW and 150 mW respectively, according to the groups). Right after the irradiation, the number of writhings was counted for 1 hour. The study was approved by Animal Ethics Committee of Federal University of Sao Carlos (# 004/2011). Results: The total number of contractions for each group was: 99 ± 57 for G1; 34 ± 19 for G2 (p<0.05), 65 ± 61 for G3, 35 ± 22 for G4 (p<0.05), 57 ± 50 for G5, 39 ± 26 for G6 e 36 ± 19 for G7. There was a significant writhings reduction in G2 (66%, p=0.04) and G4 (64%, p=0.03). Conclusions: These results suggest that infrared light, laser or LED, under low doses and low irradiance seems the best option to alleviate acute pain.
