Pain management using photobiomodulation: Mechanisms, location, and repeatability quantified by pain threshold and neural biomarkers in mice

Abstract

Photobiomodulation (PBM) is a simple, efficient and cost-effective treatment for both acute and chronic pain. We previously showed that PBM applied to the mouse head inhibited nociception in the foot. Nevertheless, the optimum parameters, location for irradiation, duration of the effect and the mechanisms of action remain unclear. In the present study, the pain threshold in the right hind paw of mice was studied, after PBM (810 nm CW laser, spot size 1 or 6 cm , 1.2-36 J/cm ) applied to various anatomical locations. The pain threshold, measured with von Frey filaments, was increased more than 3-fold by PBM to the lower back (dorsal root ganglion, DRG), as well as to other neural structures along the pathway such as the head, neck and ipsilateral (right) paw. On the other hand, application of PBM to the contralateral (left) paw, abdomen and tail had no effect. The optimal effect occurred 2 to 3 hours post-PBM and disappeared by 24 hours. Seven daily irradiations showed no development of tolerance. Type 1 metabotropic glutamate receptors decreased, and prostatic acid phosphatase and tubulin-positive varicosities were increased as shown by immunofluorescence of DRG samples. These findings elucidate the mechanisms of PBM for pain and provide insights for clinical practice.

Pulsed ND:YAG laser combined with progressive pressure release in the treatment of cervical myofascial pain syndrome: a randomized control trial

“…The infrared laser can reduce pain indirectly by modulating the inflammatory process by reducing the concentration of pro-inflammatory cytokines 26) and increasing the levels of anti-inflammatory cytokines 27) . The infrared laser stimulates nociceptors and leads to an increased pain threshold 28) . MTrPs are characterized by muscle fiber shortening, which results in impaired local circulation, leading to poor oxygen and nutrient supply 29) .…”

Photobiomodulation Decreases Hyperalgesia in Complex Regional Pain Syndrome: An Experimental Mouse Model Subjected to Nicotine

“…Of the electrophysical agents, photomodulation has relevance as a complementary treatment for CRPS, where the cellular photobiomodulation (PBMT) effects appear to reverse mitochondrial inhibition, potentiating the effects of sodium–potassium pumps and generating increases in cellular metabolism and proliferation [18]. When adenosine triphosphate is stimulated, peripheral sensitization inhibition occurs, leading to decreases in inflammatory neuropeptides and increases in serotonin and endorphin release [18–20].…”

Low‐Intensity Photobiomodulation Decreases Neuropathic Pain in Paw Ischemia‐Reperfusion and Spared Nervus Ischiadicus Injury Experimental Models

“…In addition, the increase of the pain threshold in the right hindpaw of mice (measured by von Frey filaments) was demonstrated after photobiomodulation with infrared (810 nm) applied to different anatomical locations. It was also demonstrated that type 1 metabotropic glutamate receptors decreased, and prostatic acid phosphatase and tubulin‐labeled varicosities were increased . Other studies have shown the involvement of the opioid and serotonergic systems in different pain models .…”

“…It was also demonstrated that type 1 metabotropic glutamate receptors decreased, and prostatic acid phosphatase and tubulin-labeled varicosities were increased. 59 Other studies have shown the involvement of the opioid and serotonergic systems in different pain models. [60][61][62] However, further investigation is needed to elucidate the specific nuclei and subnuclei of the endogenous pain inhibitory system involved in this antinociceptive phenomenon.…”