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The role of reactive oxygen species in capsaicin-induced mechanical hyperalgesia and in the activities of dorsal horn neurons

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Authors
Lee, Inhyung; Kim, Hee Kee; Kim, Jae Hyo; Chung, Kyungsoon; Chung, Jin Mo
Issue Date
2007-03-26
Publisher
Elsevier
Citation
Pain 2007;133:9-17
Keywords
Free radicalsInflammatory painCentral sensitizationROS
Abstract
Previous findings that reactive oxygen species (ROS) are involved in neuropathic pain, mainly through spinal mechanisms, suggest that ROS may be involved in central sensitization. To investigate the possible role of ROS in central sensitization, we examined in rats the effects of ROS scavengers on capsaicin-induced secondary hyperalgesia, which is known to be mediated by central sensitization. We used two different ROS scavengers: phenyl N-tert-butylnitrone (PBN) and 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPOL). Intradermal capsaicin injection (20 μg in 20 μl olive oil) into the hind paw produced primary and secondary hyperalgesia. A systemic administration of PBN (100 mg/kg, i.p.) or TEMPOL (200 mg/kg, i.p.) alleviated capsaicin-induced secondary, but not primary, hyperalgesia. Intrathecal injection of PBN (1 mg inof vertinary Surgery/anesthesiology, College of vetrinary Medic 50 μl saline) greatly reduced hyperalgesia, whereas intracerebroventricular or intradermal injection of PBN produced only a minor analgesic effect, suggesting that PBN takes effect mainly through the spinal cord. Electrophysiological recordings from wide dynamic range (WDR) neurons in the dorsal horn showed that intradermal capsaicin enhanced the evoked responses to peripheral stimuli; systemic PBN or TEMPOL restored the responses to normal levels. Removal of ROS thus restored the responsiveness of spinal WDR neurons to normal levels, suggesting that ROS is involved in central sensitization, at least in part by sensitizing WDR neurons.
ISSN
0304-3959
http://dx.doi.org/10.1016/j.pain.2007.01.035
Language
English
URI
http://hdl.handle.net/10371/7609
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College of Veterinary Medicine (수의과대학)Dept. of Veterinary Medicine (수의학과)Journal Papers (저널논문_수의학과)
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