title: Role of adenosine receptors in the anti-nociceptive effects of allopurinol in mice.
abstract: BACKGROUND
  Inhibition of xanthine oxidase by allopurinol increases hypoxanthine and xanthine, which are converted to purines, including the inhibitory neuromodulator adenosine.
  
  
  OBJECTIVE
  We aimed to investigate the antinociceptive effects of allopurinol in thermal and chemical pain models in mice and to evaluate its possible antinociceptive mechanism by using selective adenosine receptors A1, A2A antagonists in mice.
  
  
  METHODS
  Sixty four adult male mice were used. Mice received an intraperitoneal injection of vehicle or allopurinol (50-200 mg/kg). Assessment of antinociceptive effects and locomotor activity were performed in three models of acute pain; a thermal model and two chemical model.
  
  
  RESULTS
  Allopurinol presented dose-dependent antinociceptive effects in all models with no obvious motor deficits. The opioid antagonist naloxone did not reverse these effects. The selective A1 antagonist, DPCPX, and the selective A2A antagonist, ZM241385, completely prevented allopurinol-induced antinociception.
  
  
  CONCLUSIONS
  Allopurinol-induced antinociception may be related to adenosine accumulation. Allopurinol seems to be well tolerated with no locomotor side effects at high doses and it may be useful to treat pain syndromes.
authors.affiliation: Department of Pharmacology, Suez Canal University, Ismailia, Egypt. sohaessawy@yahoo.com
authors.forename: S S
authors.initials: SS
authors.lastname: Essawy
authors.forename: A A
authors.initials: AA
authors.lastname: Elbaz
mesh_terms: D058916:Adenosine A1 Receptor Antagonists / Q000494:pharmacology; D058917:Adenosine A2 Receptor Antagonists / Q000494:pharmacology; D000493:Allopurinol / Q000494:pharmacology*; D000700:Analgesics; D000818:Animals; D002211:Capsaicin; D006358:Hot Temperature; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects; D010146:Pain / Q000139:chemically induced / Q000517:prevention & control; D010147:Pain Measurement / Q000187:drug effects; D004856:Postural Balance / Q000187:drug effects; D011597:Psychomotor Performance / Q000187:drug effects; D043705:Receptor, Adenosine A2A / Q000187:drug effects; D018047:Receptors, Purinergic P1 / Q000187:drug effects*
chemical_list: D058916:Adenosine A1 Receptor Antagonists; D058917:Adenosine A2 Receptor Antagonists; D000700:Analgesics; D043705:Receptor, Adenosine A2A; D018047:Receptors, Purinergic P1; D000493:Allopurinol; D002211:Capsaicin