title: Roles of adenosine and serotonin receptors on the antinociception of sildenafil in the spinal cord of rats.
abstract: OBJECTIVE
  The phosphodiesterase 5 inhibitor sildenafil has antinociceptive effects, mediated by an increase in cGMP. This study examined the role of spinal adenosine and serotonin receptors played in the antinociceptive effects of intrathecal sildenafil.
  
  
  METHODS
  Intrathecal catheters were inserted into the subarachnoid space of Sprague-Dawley male rats as a drug delivery device. Pain was induced by injecting formalin into the plantar surface of rats and observing nociceptive behavior (flinching response) for 60 minutes. Then, the effects of intrathecal adenosine and serotonin receptor antagonists on the antinociceptive activity of intrathecal sildenafil were examined.
  
  
  RESULTS
  Intrathecal sildenafil suppressed the flinching response in a dose-dependent manner during phases 1 and 2 in the formalin test. Both CGS 15943 and dihydroergocristine decreased the antinociceptive effects of sildenafil during phases 1 and 2 in the formalin test.
  
  
  CONCLUSIONS
  Intrathecal sildenafil effectively attenuated the pain evoked by formalin injection. Both adenosine and serotonin receptors may be involved in the antinociceptive action of sildenafil at the spinal level.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Chonnam National University Medical School, Dong-gu, Gwangju, Korea.
authors.forename: Hyung Gon
authors.initials: HG
authors.lastname: Lee
authors.forename: Woong Mo
authors.initials: WM
authors.lastname: Kim
authors.forename: Cheon Hee
authors.initials: CH
authors.lastname: Park
authors.forename: Myung Ha
authors.initials: MH
authors.lastname: Yoon
mesh_terms: D000241:Adenosine / Q000378:metabolism; D000700:Analgesics / Q000627:therapeutic use*; D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism; D025442:Dihydroergocristine / Q000494:pharmacology; D007278:Injections, Spinal; D008297:Male; D010146:Pain / Q000188:drug therapy*; D010879:Piperazines / Q000494:pharmacology*; D011687:Purines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018047:Receptors, Purinergic P1 / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000378:metabolism*; D000068677:Sildenafil Citrate; D013116:Spinal Cord / Q000378:metabolism*; D013450:Sulfones / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000627:therapeutic use
chemical_list: D000700:Analgesics; D010879:Piperazines; D011687:Purines; D018047:Receptors, Purinergic P1; D011985:Receptors, Serotonin; D013450:Sulfones; D014665:Vasodilator Agents; D025442:Dihydroergocristine; D000068677:Sildenafil Citrate; D006152:Cyclic GMP; D000241:Adenosine