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Neurophotonics. 2016 Jan;3(1):015003. doi: 10.1117/1.NPh.3.1.015003. Epub 2016 Jan 25.

Transcranial low-level laser therapy (810 nm) temporarily inhibits peripheral nociception: photoneuromodulation of glutamate receptors, prostatic acid phophatase, and adenosine triphosphate.

Author information

1
Massachusetts General Hospital, Wellman Center for Photomedicine, BAR414, 40 Blossom Street, Boston, Massachusetts 02114, United States; University of São Paulo, Institute of Physics, Laboratory of Radiation Dosimetry and Medical Physics, Rua do Matão, Travessa R, 187, Cidade Universitária, São Paulo, Brazil; Bright Photomedicine Ltd., CIETEC Building, 2242 Lineu Prestes, São Paulo 05508-000, Brazil.
2
Massachusetts General Hospital, Wellman Center for Photomedicine, BAR414, 40 Blossom Street, Boston, Massachusetts 02114, United States; Federal University of São Carlos, Department of Physical Therapy, Laboratory of Electro-Thermo-Phototherapy, Street Washington Luis, km 235. Monjolinho, São Carlos, São Paulo 13565-905, Brazil; Federal University of São Carlos, Post-Graduation Program in Biotechnology, Street Washington Luis, km 235. Monjolinho, São Carlos, São Paulo 13560-000, Brazil; University of São Paulo, Optics Group, Physics Institute of São Carlos, Street Miguel Petroni, 146-Jardim Bandeirantes, São Carlos, São Paulo 13560-970, Brazil.
3
Massachusetts General Hospital , Wellman Center for Photomedicine, BAR414, 40 Blossom Street, Boston, Massachusetts 02114, United States.
4
Massachusetts General Hospital, Wellman Center for Photomedicine, BAR414, 40 Blossom Street, Boston, Massachusetts 02114, United States; Federal University of Rio de Janeiro, Carlos Chagas Filho, 373-Cidade Universitária, Rio de Janeiro, RJ 21941-170, Brazil.
5
University of São Paulo , Institute of Physics, Laboratory of Radiation Dosimetry and Medical Physics, Rua do Matão, Travessa R, 187, Cidade Universitária, São Paulo, Brazil.
6
Massachusetts General Hospital, Wellman Center for Photomedicine, BAR414, 40 Blossom Street, Boston, Massachusetts 02114, United States; Harvard Medical School, Department of Dermatology, 50 Staniford Street #807, Boston, Massachusetts 02114, United States; Harvard-MIT, Division of Health Sciences and Technology, 77 Massachusetts Avenue, E25-518, Cambridge, Massachusetts 02139, United States.

Abstract

Photobiomodulation or low-level light therapy has been shown to attenuate both acute and chronic pain, but the mechanism of action is not well understood. In most cases, the light is applied to the painful area, but in the present study we applied light to the head. We found that transcranial laser therapy (TLT) applied to mouse head with specific parameters (810 nm laser, [Formula: see text], 7.2 or [Formula: see text]) decreased the reaction to pain in the foot evoked either by pressure (von Frey filaments), cold, or inflammation (formalin injection) or in the tail (evoked by heat). The pain threshold increasing is maximum around 2 h after TLT, remains up to 6 h, and is finished 24 h after TLT. The mechanisms were investigated by quantification of adenosine triphosphate (ATP), immunofluorescence, and hematoxylin and eosin (H&E) staining of brain tissues. TLT increased ATP and prostatic acid phosphatase (an endogenous analgesic) and reduced the amount of glutamate receptor (mediating a neurotransmitter responsible for conducting nociceptive information). There was no change in the concentration of tubulin, a constituent of the cytoskeleton, and the H&E staining revealed no tissue damage. This is the first study to show inhibition of peripheral pain due to photobiomodulation of the central nervous system.

KEYWORDS:

Von Frey filaments; adenosine triphosphate; cold plate test; formalin injection; metabotropic glutamate receptor; nociception; pain threshold; photobiomodulation; prostatic acid phosphatase; tail flick test; transcranial low-level laser therapy

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