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Long-lasting antinociceptive effects of green light in acute and chronic pain in rats
AuthorIbrahim, Mohab M.
Gilbraith, Kerry B.
Chew, Lindsey A.
Malan, T. Philip
Vanderah, Todd W.
AffiliationPharmacology, College of Medicine, University of Arizona
Anesthesiology, College of Medicine, University of Arizona
MetadataShow full item record
PublisherLIPPINCOTT WILLIAMS & WILKINS
CitationLong-lasting antinociceptive effects of green light in acute and chronic pain in rats 2017, 158 (2):347 PAIN
Rights© 2017 International Association for the Study of Pain
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractTreatments for chronic pain are inadequate, and new options are needed. Nonpharmaceutical approaches are especially attractive with many potential advantages including safety. Light therapy has been suggested to be beneficial in certain medical conditions such as depression, but this approach remains to be explored for modulation of pain. We investigated the effects of light-emitting diodes (LEDs), in the visible spectrum, on acute sensory thresholds in naive rats as well as in experimental neuropathic pain. Rats receiving green LED light (wavelength 525 nm, 8 h/d) showed significantly increased paw withdrawal latency to a noxious thermal stimulus; this antinociceptive effect persisted for 4 days after termination of last exposure without development of tolerance. No apparent side effects were noted and motor performance was not impaired. Despite LED exposure, opaque contact lenses prevented antinociception. Rats fitted with green contact lenses exposed to room light exhibited antinociception arguing for a role of the visual system. Antinociception was not due to stress/anxiety but likely due to increased enkephalins expression in the spinal cord. Naloxone reversed the antinociception, suggesting involvement of central opioid circuits. Rostral ventromedial medulla inactivation prevented expression of light-induced antinociception suggesting engagement of descending inhibition. Green LED exposure also reversed thermal and mechanical hyperalgesia in rats with spinal nerve ligation. Pharmacological and proteomic profiling of dorsal root ganglion neurons from green LED-exposed rats identified changes in calcium channel activity, including a decrease in the N-type (CaV2.2) channel, a primary analgesic target. Thus, green LED therapy may represent a novel, nonpharmacological approach for managing pain.
Note12 month embargo; Available online 19 November 2016
VersionFinal accepted manuscript
SponsorsCareer Development Award from the University of Arizona Health Sciences; Children's Tumor Foundation NF1 Synodos grant; start- up seed fund; Young Investigator Award from the Children's Tumor Foundation