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October 26, 2005
9:00:00 AM - 11:00:00 AM
Hall C4
Laser Irradiation Leads to Endogenous Opioid Peptides Gene Expression in the Leukocyte
Satoshi Hagiwara, M.D., Hideo Iwasaka, M.D., Ph.D., Tomoko Uchinou, M.D., Ph.D., Hiroshi Miyakawa, M.D., Ph.D., Takayuki Noguchi, M.D., Ph.D.
Department of Anesthesiology, Oita University Faculty of Medicine, Oita Prefecture, Japan
Introduction: Laser irradiation has been reported to reduce injury, promote regeneration, and analgesia. In the pain clinic, the treatment of the laser irradiation is a safe and effective. So, it is the very useful tool. While the mechanism is unknown, one hypothesis is that laser produces endogenous opioid peptides in immune cells, which play an important role of local analgesia. Pro-opiomelanocortin (POMC) is the precursor to beta-endorphin, which is a prominent peptide involved in pain. Corticotropin-releasing factor (CRF) decreases pain by stimulation of immune cells in inflamed tissue. These endogenous opioid peptides are very important to the peripheral analgesia. We therefore investigated whether laser irradiation may affect opioid peptide gene expression in the leukocyte and whether auto-transfusion of the laser irradiated blood reduces the peripheral pain.

Methods: All experiments were conducted in accordance with the Institutional Care and Use Committee. In vitro study, POMC and CRF mRNA expression was investigated in the blood of the rat exposed to laser (1000mW) for 5minutes by reverse transcription polymerase chain reaction (RT-PCR). GAPDH was also amplified with RT-PCR as an internal control. In vivo study, we investigated weather auto-transfusion of the laser irradiation blood reduces the peripheral pain. Adult male Sprague Dawley rats weighting about 300g were used. We cannurated under the general anesthesia in the right external jugular vain and performed 1000mw laser irradiation at once for 5 minutes after removal of 2ml of the blood and this five times in total. After laser irradiation, we injected Freumd's complete adjuvant (FCA) into the sole planter and did the pain evaluation by a hot planter test.

Results: POMC and CRF mRNA expression was markedly enhanced at 4 hours after laser irradiation. By the laser irradiation of the blood, a pain reduction effect was provided. At this time at the inflammatory spot, the manifestation and augmentation of Beta-endorphin was confirmed by the laser irradiation.

Discussions: The present findings demonstrate that POMC and CRF genes are activated by the leukocyte exposure to laser. Expression of opioid peptides by the immune cells is very important in the local analgesic effect. The current data may suggest that the laser irradiation of the blood will probably reduce the various pain (ex. Post-operative pain) and the new peripheral pain control system may develop by the laser irradiation of the blood.

Anesthesiology 2005; 103: A1093