title: Antinociceptive effect of astragalosides and its mechanism of action.
abstract: OBJECTIVE
  To study the effect and mechanism of astragalosides (AST) related to the antinociceptive activity.
  
  
  METHODS
  The standardized formalin test was performed to induce the direct stimulation of nociceptors followed by inflammatory process in the Kunming strain mice. The involvement of opioid and nitric oxide was studied by subcutaneous injection of morphine with/without naloxone 30 min before formalin test, or peritoneal injection of L-arginine with/without L-NAME 20 min before formalin.
  
  
  RESULTS
  AST 20, 40, and 80 mg/kg significantly lowered pain score of the second phase of formalin response as compared with control group (P<0.01). The maximum analgesic effect of AST 40 mg/kg was found at 4 h after the administration of AST (34.4 % inhibition at the second phase). Injection of morphine 5 mg/kg significantly inhibited pain response of both phases (P<0.01) and this was reversed by naloxone 2 mg/kg (P<0.01). However, naloxone did not alter the effect of AST on the second phase. Antinociceptive effect of AST 40 mg/kg was partially blocked by L-arginine 400 or 800 mg/kg (P<0.01).
  
  
  CONCLUSIONS
  AST has an antinociceptive effect on formalin test in mice that is not mediated by the endogenous opioid system but related to its inhibitory effect on the production of NO.
authors.affiliation: Institute of Clinical Pharmacology, Anhui Medical University, Hefei 230032, China; Department of Surgery, The Chinese University of Hong Kong, Hong Kong SAR, China. s002316@mailserv.cuhk.edu.hk
authors.forename: Q
authors.initials: Q
authors.lastname: Yang
authors.forename: J T
authors.initials: JT
authors.lastname: Lu
authors.forename: A W
authors.initials: AW
authors.lastname: Zhou
authors.forename: B
authors.initials: B
authors.lastname: Wang
authors.forename: G W
authors.initials: GW
authors.lastname: He
authors.forename: M Z
authors.initials: MZ
authors.lastname: Chen
mesh_terms: D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D000818:Animals; D008297:Male; D051379:Mice; D009270:Naloxone / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D009619:Nociceptors / Q000187:drug effects*; D010147:Pain Measurement; D012503:Saponins / Q000494:pharmacology*; D014315:Triterpenes / Q000494:pharmacology*
chemical_list: D018712:Analgesics, Non-Narcotic; D012503:Saponins; D014315:Triterpenes; D009569:Nitric Oxide; D009270:Naloxone; C052064:astragaloside A