title: Sucrose-induced analgesia in mice: role of nitric oxide and opioid receptor-mediated system.
abstract: BACKGROUND
  The mechanism of action of sweet substance-induced analgesia is thought to involve activation of the endogenous opioid system. The nitric oxide (NO) pathway has a pivotal role in pain modulation of analgesic compounds such as opioids.
  
  
  OBJECTIVE
  We investigated the role of NO and the opioid receptor-mediated system in the analgesic effect of sucrose ingestion in mice.
  
  
  METHODS
  We evaluated the effect of intraperitoneal administration of 10 mg/kg of NO synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME) and 20 mg/kg of opioid receptor antagonist, naltrexone on the tail flick response in sucrose ingesting mice.
  
  
  RESULTS
  Sucrose ingestion for 12 days induced a statistically significant increase in the latency of tail flick response which was unmodified by L-NAME, but partially inhibited by naltrexone administration.
  
  
  CONCLUSIONS
  Sucrose-induced nociception may be explained by facilitating the release of endogenous opioid peptides. Contrary to some previously studied pain models, the NO/cyclic guanosine monophosphate (cGMP) pathway had no role in thermal hyperalgesia in our study. We recommend further studies on the involvement of NO in other animals and pain models.
authors.affiliation: Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran ; Students' Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Abtin
authors.initials: A
authors.lastname: Shahlaee
authors.affiliation: Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Farahanchi
authors.affiliation: Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Shiva
authors.initials: S
authors.lastname: Javadi
authors.affiliation: Department of Pharmacology, Lorestan University of Medical Sciences, Faculty of Medicine, Khoram Abad, Iran.
authors.forename: Bahram
authors.initials: B
authors.lastname: Delfan
authors.affiliation: Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Ahmad Reza
authors.initials: AR
authors.lastname: Dehpour
mesh_terms: D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D008297:Male; D051379:Mice; D009569:Nitric Oxide / Q000502:physiology*; D011957:Receptors, Opioid / Q000502:physiology*; D013395:Sucrose / Q000494:pharmacology*
chemical_list: D000700:Analgesics; D011957:Receptors, Opioid; D009569:Nitric Oxide; D013395:Sucrose
keywords: N-nitro-L-arginine methyl ester; Naltrexone; opioid; tail flick test