title: Analgesic effect of agmatine and its enhancement on morphine analgesia in mice and rats.
abstract: OBJECTIVE
  To study the effect of agmatine on pain and morphine analgesia.
  
  
  METHODS
  The effect of agmatine on pain was observed in mouse heat radiant tail-flick test, mouse acetic acid writhing test, and rat 4% saline test. Its enhancing effect on analgesia of morphine and clonidine was assessed in rat and mouse heat radiant tail-flick tests.
  
  
  RESULTS
  Agmatine did not significantly prolong tail-flick latency of mice, but reduced the number of acetic acid-induced writhing of mice and inhibited writhing responses to saline completely. It potentiated the analgesic effects of morphine and clonidine in dose-dependent manner and decreased the analgesic ED50 of morphine and clonidine by more than 75% in mouse heat radiant tail-flick test. These effects of agmatine were antagonized by idazoxan.
  
  
  CONCLUSIONS
  Agmatine has weak analgesic effects and potentiates morphine and clonidine analgesia by activation of imidazoline receptors.
authors.affiliation: Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing, China.
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: G
authors.initials: G
authors.lastname: Pei
authors.forename: B Y
authors.initials: BY
authors.lastname: Qin
mesh_terms: D000376:Agmatine / Q000494:pharmacology*; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004357:Drug Synergism; D005260:Female; D007093:Imidazoles; D054755:Imidazoline Receptors; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011955:Receptors, Drug / Q000187:drug effects
chemical_list: D018712:Analgesics, Non-Narcotic; D000701:Analgesics, Opioid; D007093:Imidazoles; D054755:Imidazoline Receptors; D011955:Receptors, Drug; D000376:Agmatine; D009020:Morphine; D003000:Clonidine