title: Effects of phosphodieastrase type 5 inhibitions on morphine withdrawal symptoms in mice.
abstract: BACKGROUND
  Chronic morphine exposure creates dependence and, upon cessation, withdrawal symptoms. Studies indicate the phosphodiesterase type 5 (PDE5) inhibitor sildenafil may provide centrally mediated benefits against withdrawal, and therefore, this study evaluated morphine withdrawal signs in dependent mice with and without sildenafil treatment.
  
  
  METHODS
  Dependence was induced by repeated treatments with morphine over 5 consecutive days. The morphine-dependent mice received sildenafil (1, 5, 10, or 20 mg/kg, i.p.) 15 min prior to the precipitation of morphine withdrawal. On the last day, naloxone was injected 2 hours after the last morphine injection, and withdrawal signs were evaluated for 30 min after naloxone injection.
  
  
  RESULTS
  The administration of sildenafil reduced all of the morphine withdrawal symptoms.
  
  
  CONCLUSIONS
  The administration of sildenafil diminished morphine withdrawal signs in morphine-dependent mice. We hypothesize that the mechanism involves enhanced cyclic guanosine monophosphate (cGMP) activity, but further studies are recommended for a better understanding.
authors.affiliation: Islamic Azad University, Hamadan Branch (Irán).
authors.forename: Minoo
authors.initials: M
authors.lastname: Mahmoodi
authors.forename: Siamak
authors.initials: S
authors.lastname: Shahidi
authors.forename: Nasrin
authors.initials: N
authors.lastname: Hashemi-Firouzi
mesh_terms: D000818:Animals; D008297:Male; D051379:Mice; D009020:Morphine / Q000009:adverse effects*; D058986:Phosphodiesterase 5 Inhibitors / Q000627:therapeutic use*; D000068677:Sildenafil Citrate / Q000627:therapeutic use*; D013375:Substance Withdrawal Syndrome / Q000188:drug therapy*
chemical_list: D058986:Phosphodiesterase 5 Inhibitors; D009020:Morphine; D000068677:Sildenafil Citrate