title: Rewarding properties of sildenafil citrate in mice: role of the nitric oxide-cyclic GMP pathway.
abstract: BACKGROUND
  Sildenafil citrate is widely prescribed for erectile dysfunction and acts by inhibiting phosphodiesterase type-5, resulting in accumulation of cyclic-guanosine monophosphate (cGMP) via activation of nitric oxide synthase (NOS). The nitric oxide (NO) system is relevant to the rewarding effects of various drugs of abuse. Several epidemiologic studies indicate that sildenafil is abused in a recreational fashion.
  
  
  OBJECTIVE
  In the present study, the rewarding properties of sildenafil and probable involvement of the NO-cGMP pathway were investigated in adult male NMRI mice.
  
  
  METHODS
  The ability of sildenafil citrate (1-40 mg/kg) to produce conditioned place preference (CPP) was studied in an unbiased CPP paradigm. The effects of NO precursor L-arginine, nonselective NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME), and the inhibitor of guanylyl cyclase methylene blue (MB) on sildenafil-induced CPP were assessed.
  
  
  RESULTS
  Mice that received sildenafil (20 and 40 mg/kg) in one environment during conditioning phase displayed a preference for this environment. Both L-NAME (5 mg/kg) and MB (1 mg/kg) in combination with sildenafil (20 mg/kg) suppressed the acquisition of sildenafil-induced place preference. Lower and per se noneffective dose of sildenafil (10 mg/kg) and L-arginine (60 mg/kg), when coadministered, exerted a significant place conditioning.
  
  
  CONCLUSIONS
  Sildenafil shows rewarding properties that may involve the NO-cGMP pathway.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Tehran University of Medical Sciences, P.O. Box 13145-784, Tehran, Iran.
authors.forename: Pouya
authors.initials: P
authors.lastname: Tahsili-Fahadan
authors.forename: Noushin
authors.initials: N
authors.lastname: Yahyavi-Firouz-Abadi
authors.forename: Amir Hossein
authors.initials: AH
authors.lastname: Orandi
authors.forename: Behnaz
authors.initials: B
authors.lastname: Esmaeili
authors.forename: Zahra
authors.initials: Z
authors.lastname: Basseda
authors.forename: Ahmad Reza
authors.initials: AR
authors.lastname: Dehpour
mesh_terms: D000818:Animals; D001120:Arginine / Q000494:pharmacology; D003213:Conditioning, Psychological / Q000187:drug effects*; D006152:Cyclic GMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D008297:Male; D008751:Methylene Blue / Q000494:pharmacology; D051379:Mice; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011687:Purines; D012201:Reward; D000068677:Sildenafil Citrate; D013450:Sulfones
chemical_list: D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D009569:Nitric Oxide; D001120:Arginine; D000068677:Sildenafil Citrate; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D008751:Methylene Blue; D019331:NG-Nitroarginine Methyl Ester