title: The analgesic effect of paeoniflorin on neonatal maternal separation-induced visceral hyperalgesia in rats.
abstract: Paeoniflorin (PF) is one of the principle active ingredients of the root of Paeonia lactiflora Pall (family Ranunculaceae), a Chinese herb traditionally used to relieve pain, especially visceral pain. The present study aimed to investigate both the effect of PF on neonatal maternal separation-induced visceral hyperalgesia in rats and the mechanism by which such effect is exerted. A dose-dependent analgesic effect was produced by PF (45, 90, 180, and 360 mg/kg i.p.). Centrally administered PF (4.5 mg/kg i.c.v) also produced a significant analgesic effect. The analgesic effect of PF (45 mg/kg i.p.) was maximal at 30 minutes after administration. Furthermore, it was found that nor-binaltorphimine (nor-BNI, 3 mg/kg i.p.), dl-alpha-methyltyrosine (alpha-AMPT, 250 mg/kg i.p.), and yohimbine (3 mg/kg i.p.) could block the analgesic effect of PF (45 mg/kg i.p.). Time course determination of PF in brain nuclei showed that the maximal concentration of PF was 30 minutes after intraperitoneal administration of PF (180 mg/kg) in cerebral nuclei, involving the amygdala, hypothalamus, thalamus, and cortex. These data indicate that PF has an analgesic effect on visceral pain in rats with neonatal maternal separation and that this effect may be mediated by kappa-opioid receptors and alpha(2)-adrenoceptors in the central nervous system.
  
  
  CONCLUSIONS
  This study demonstrates that PF has an analgesic effect on pain in visceral hyperalgesic rats. These results suggest that PF might be potentially useful in clinical therapy for irritable bowel syndrome as a pharmacological agent in alleviating visceral pain.
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China.
authors.forename: Xiao-Jun
authors.initials: XJ
authors.lastname: Zhang
authors.forename: Zhi
authors.initials: Z
authors.lastname: Li
authors.forename: Wai-Mui
authors.initials: WM
authors.lastname: Leung
authors.forename: Liang
authors.initials: L
authors.lastname: Liu
authors.forename: Hong-Xi
authors.initials: HX
authors.lastname: Xu
authors.forename: Zhao-Xiang
authors.initials: ZX
authors.lastname: Bian
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use*; D001565:Benzoates / Q000627:therapeutic use*; D001952:Bridged-Ring Compounds / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D004333:Drug Administration Routes; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005960:Glucosides / Q000627:therapeutic use*; D006930:Hyperalgesia / Q000188:drug therapy*; D008297:Male; D008426:Maternal Deprivation; D039821:Monoterpenes; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D015016:Yohimbine / Q000494:pharmacology; D019805:alpha-Methyltyrosine / Q000494:pharmacology; D006027:Glycosides
chemical_list: D000317:Adrenergic alpha-Antagonists; D000894:Anti-Inflammatory Agents, Non-Steroidal; D001565:Benzoates; D001952:Bridged-Ring Compounds; D004791:Enzyme Inhibitors; D005960:Glucosides; D039821:Monoterpenes; D009271:Naltrexone; D009292:Narcotic Antagonists; D015016:Yohimbine; D019805:alpha-Methyltyrosine; C015423:peoniflorin; D006027:Glycosides; C051844:norbinaltorphimine