Targeting pain and inflammation: A comparative study of photobiomodulation with 532 and 660 nm lasers in rats

This study evaluated the analgesic and anti-inflammatory effects of photobiomodulation (PBM) using 532 nm (green) and 660 nm (red) low-power lasers in an animal model of acute postoperative pain. Forty-five Wistar rats underwent a 1 cm surgical incision on the right hind paw and were randomly assigned to three groups: red laser (RL, 660 nm, 100 mW, 5 J, 167 J/cm²), green laser (GL, 532 nm, 70 mW, 4.97 J, 166 J/cm²), and control (LO, no irradiation). PBM was applied immediately and at 1-, 3-, 6-, and 24-h postsurgery, and pain levels were assessed using von Frey's electronic analgesimeter. Inflammatory cytokines (TNF-α, IL-1β, CGRP, and Substance P) were measured by ELISA. Results showed that both RL and GL were significantly more effective than the control group in reducing pain and inflammation. RL provided superior analgesia, increasing pain tolerance to 690.54 ± 50.20 g at 24 h, reaching levels comparable to the non-incised paw (p < 0.001). GL demonstrated greater anti-inflammatory effects, significantly reducing TNF-α levels at 1 h (p < 0.05) and 24 h and maintaining lower IL-1β and CGRP levels. RL also modulated Substance P levels, correlating with its stronger analgesic effect. These findings suggest that RL is preferable for direct pain relief, while GL is more effective in modulating inflammatory responses. Given the statistically significant improvement in pain control and inflammatory marker modulation, PBM using these wavelengths could be a valuable adjunct therapy for postoperative pain management and enhanced healing in surgical patients. Future studies should explore synergistic PBM protocols combining both wavelengths to optimize clinical outcomes.