title: High-dose pentazocine antagonizes the antinociception induced by high-dose morphine.
abstract: OBJECTIVE
  To investigate the effects of high doses of pentazocine on antinociception induced by a high dose of morphine and the role of the kappa-opioid receptors (KORs) in these effects in mice.
  
  
  METHODS
  Sixty-six C57BL/6J mice were pretreated with a KOR antagonist, nor-binaltorphimine (nor-BNI) (10mg·kg(-1)), or a normal saline placebo. All the mice received a subcutaneous injection of morphine (10mg·kg(-1)) 120min later and different doses of pentazocine (3, 10, 30, 56, 100mg·kg(-1)) or a normal saline placebo. A tail pressure test, hot plate test and tail flick test were performed before and at 30, 60, 90 and 120min after the injection of morphine.
  
  
  RESULTS
  The tail pressure test, hot plate test and tail flick test showed that pentazocine at doses of 10 to 100mg·kg(-1), but not at 3mg·kg(-1), had significant antagonizing effects on the antinociception induced by high-dose morphine to mechanical and thermal pain, and nor-BNI did not affect antinociception in combination with pentazocine at 10 to 100mg·kg(-1) and morphine at 10mg·kg(-1).
  
  
  CONCLUSIONS
  High-doses of pentazocine antagonize the antinociception induced by a high-dose of morphine in a dose-dependent manner, and this antagonistic effect is not associated with the activation of KORs.
authors: Department of Anesthesiology, Guangdong Second Provincial People's Hospital, 466(#) Xingang Road, Guangzhou, Guangdong 510317, China; Department of Anesthesiology, First Affiliated Hospital of Sun Yat-sen University, 58(#) Zhongshan 2nd Road, Guangzhou, Guangdong 510080, China. Electronic address: shuhaihua@hotmail.com.
authors: Haihua
authors: H
authors: Shu
authors: Department of Gastrointestinal Surgery, First Affiliated Hospital of Sun Yat-sen University, 58(#) Zhongshan 2nd Road, Guangzhou, Guangdong 510080, China; Centre of Gastric Cancer, First Affiliated Hospital of Sun Yat-sen University, 58(#) Zhongshan 2nd Road, Guangzhou, Guangdong 510080, China.
authors: Zhao
authors: Z
authors: Wang
authors: Department of Anesthesiology, First Affiliated Hospital of Sun Yat-sen University, 58(#) Zhongshan 2nd Road, Guangzhou, Guangdong 510080, China.
authors: Fang
authors: F
authors: Ye
authors: Department of Anesthesiology, First Affiliated Hospital of Sun Yat-sen University, 58(#) Zhongshan 2nd Road, Guangzhou, Guangdong 510080, China.
authors: Qiaobo
authors: Q
authors: Li
authors: Department of Anesthesiology, First Affiliated Hospital of Sun Yat-sen University, 58(#) Zhongshan 2nd Road, Guangzhou, Guangdong 510080, China.
authors: Yunling
authors: Y
authors: Dou
authors: Department of Anesthesiology, First Affiliated Hospital of Sun Yat-sen University, 58(#) Zhongshan 2nd Road, Guangzhou, Guangdong 510080, China.
authors: Yibin
authors: Y
authors: Lin
authors: Department of Anesthesiology, First Affiliated Hospital of Sun Yat-sen University, 58(#) Zhongshan 2nd Road, Guangzhou, Guangdong 510080, China.
authors: Wenqi
authors: W
authors: Huang
authors: Department of Anesthesiology, Guangdong Second Provincial People's Hospital, 466(#) Xingang Road, Guangzhou, Guangdong 510317, China.
authors: Xiaoshan
authors: X
authors: Xiao
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D010146:Pain / Q000188:drug therapy*; D010423:Pentazocine / Q000008:administration & dosage / Q000494:pharmacology*; D017473:Receptors, Opioid, kappa / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000701:Analgesics, Opioid; D017473:Receptors, Opioid, kappa; C051844:norbinaltorphimine; D009271:Naltrexone; D009020:Morphine; D010423:Pentazocine
keywords: Antinociception; Kappa-opioid receptor; Morphine; Mu-opioid receptor; Pentazocine