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Anesth Analg 2008; 107:1058-1063
© 2008 International Anesthesia Research Society
doi: 10.1213/ane.0b013e31817ee43e
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ANALGESIA

Pre-Irradiation of Blood by Gallium Aluminum Arsenide (830 nm) Low-Level Laser Enhances Peripheral Endogenous Opioid Analgesia in Rats

Satoshi Hagiwara, MD, PhD, Hideo Iwasaka, MD, PhD, Akira Hasegawa, MD, and Takayuki Noguchi, MD, PhD

From the Department of Brain and Nerve Science, Anesthesiology, Oita University Faculty of Medicine, Idaigaoka-Hasamamachi-Yufu City-Oita, Japan.

Address correspondence and reprint requests to Satoshi Hagiwara, PhD, Department of Brain and Nerve Science, Anesthesiology, Oita University Faculty of Medicine, 1-1 Idaigaoka-Hasamamachi-Yufu City-Oita 879-5593, Japan. Address e-mail to saku{at}med.oita-u.ac.jp.

Abstract

BACKGROUND: Low-level laser therapy (LLLT) has been reported to relieve pain, free of side effects. However, the mechanisms underlying LLLT are not well understood. Recent studies have also demonstrated that opioid-containing immune cells migrate to inflamed sites and release β-endorphins to inhibit pain as a mode of peripheral endogenous opioid analgesia. We investigated whether pre-irradiation of blood by LLLT enhances peripheral endogenous opioid analgesia.

METHODS: The effect of LLLT pretreatment of blood on peripheral endogenous opioid analgesia was evaluated in a rat model of inflammation. Additionally, the effect of LLLT on opioid production was also investigated in vitro in rat blood cells. The expression of the β-endorphin precursors, proopiomelanocortin and corticotrophin releasing factor, were investigated by reverse transcription polymerase chain reaction.

RESULTS: LLLT pretreatment produced an analgesic effect in inflamed peripheral tissue, which was transiently antagonized by naloxone. Correspondingly, β-endorphin precursor mRNA expression increased with LLLT, both in vivo and in vitro.

CONCLUSION: These findings suggest that that LLLT pretreatment of blood induces analgesia in rats by enhancing peripheral endogenous opioid production, in addition to previously reported mechanisms.






Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press
Copyright © 2008 by the International Anesthesia Research Society.