title: Analgesic effects of melatonin on post-herpetic neuralgia.
abstract: OBJECTIVE
  This study aims to explore the analgesic effects of melatonin on post-herpetic neuralgia and its possible mechanism.
  
  
  METHODS
  A total of 48 PHN Wistar rats were divided into 4 groups randomly: Normal, PHN, PHN+MT and naloxone, 4P-PDOT or L-arginine+120 mg/kg MT (C). Heat pain latency was determined after MT injection for 20 min, 40 min, 80 min and 120 min respectively. The expression levels of δ receptor and MT2 receptor in different tissues of rats were detected by RT-PCR method. NO content was determined.
  
  
  RESULTS
  Heat pain latency in PHN rats were lower than that of control group (P<0.05), MT could increase the heat pain latency with dose-dependent, while naloxone, 4P-PDOT and L-arginine could reverse the analgesic effect of MT (P<0.05). The expression levels of δ receptor and MT2 receptor in spinal cord, hypothalamus and hippocampus in PHN+MT (120 mg/kg, i. p.) group were significantly higher than that of PHN group (P<0.05). The NO levels in the brain and spinal cord tissues in PHN group were higher than that of PHN+MT (120 mg/kg) group (P<0.05).
  
  
  CONCLUSIONS
  MT had significant analgesic effects in the treatment of PHN, and its mechanism was closely related with δopioid receptor, NO and MT2 receptor.
authors.affiliation: Department of Anesthesiology, Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Center, West China Hospital, Sichuan University Chengdu, Sichuan, China ; Department of Anesthesia, Guizhou Provincial Peopleas Hospital Guiyang 550002, China.
authors.forename: Yun-Kun
authors.initials: YK
authors.lastname: Deng
authors.affiliation: Department of Anesthesia, Guizhou Provincial Peopleas Hospital Guiyang 550002, China.
authors.forename: Ji-Fei
authors.initials: JF
authors.lastname: Ding
authors.affiliation: Department of Anesthesiology, Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Center, West China Hospital, Sichuan University Chengdu, Sichuan, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Cardiology, Guizhou Provincial Peopleas Hospital Guiyang 550002, China.
authors.forename: Yong-Yao
authors.initials: YY
authors.lastname: Yang
keywords: MT2 receptor; Melatonin (MT); analgesia; nitric oxide; δopioid receptor