Abstract
Low-level laser acupuncture (LLLA) produces photobiomodulation through acupuncture point and is an alternative to low-level laser therapy. Although the analgesic effect of LLLA on chronic pain has been proven, its effect on acute postincisional pain has yet to be investigated. A plantar incision (PI) model was used to mimic human postsurgical pain. Male adult rats received GaAlAs laser irradiation at the right ST36 acupoint immediately after operation and on the following 4 days. Three laser treatment groups (two red laser groups with a 30- or 15-min treatment duration and one 30-min near-infrared laser group) were compared with sham LLLA and naive groups and an electroacupuncture (EA) group (separate study). Behavioral withdrawal thresholds of both hind paws were measured before and after incision. Expression of mitogen-activated protein kinases (p-ERK and p-p38), inducible nitric oxide synthase (iNOS), and tumor necrosis factor (TNF) in the spinal cord was analyzed. All three LLLA treatments attenuated post-PI tactile allodynia in the ipsilateral paw, but only the 30-min red laser treatment affected the contralateral paw and had similar efficacy to that of EA. All laser treatments barely reduced heat hyperalgesia in both hind paws. At 3 days after PI, the 30-min red laser group showed reversed increases of PI-induced p-ERK, p-p38, and iNOS but not TNF expression in the spinal cord. Repetitive LLLA treatments ameliorated PI-induced mechanical pain. The inhibition of multiple sensitization signals highlights the unique clinical role of LLLA. Thus, LLLA is an alternative to EA as an adjuvant for postoperative pain control.
Highlights
Low-level laser acupuncture (LLLA) produces photobiomodulation through acupuncture point and is an alternative to low-level laser therapy
Some LLLA studies have assessed its application for postoperative pain [3, 9], but these studies were mostly limited to dental, orofacial, and small incision surgeries
Tactile allodynia and heat hyperalgesia in the right hind paw persisted until day 3 after plantar incision (PI)
Summary
Low-level laser acupuncture (LLLA) produces photobiomodulation through acupuncture point and is an alternative to low-level laser therapy. All laser treatments barely reduced heat hyperalgesia in both hind paws. At 3 days after PI, the 30-min red laser group showed reversed increases of PI-induced p-ERK, p-p38, and iNOS but not TNF expression in the spinal cord. Low-level laser therapy (LLLT), recently termed photobiomodulation, involves using a specific range of wavelengths and low power density; it has been widely used for suppressing inflammation, healing wounds, and treating neurological diseases, acute or chronic pain, and degenerative arthritis [1, 2]. Poor surgical pain control increases perioperative morbidity and induces chronic postoperative pain [5]. Some LLLA studies have assessed its application for postoperative pain [3, 9], but these studies were mostly limited to dental, orofacial, and small incision surgeries. Whether LLLA exerts equal analgesic effects as LLLT and EA remains unclear
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