title: Antinociception induced by acute oral administration of sweet substance in young and adult rodents: the role of endogenous opioid peptides chemical mediators and μ(1)-opioid receptors.
abstract: The present work aimed to investigate the effects of acute sucrose treatment on the perception of painful stimuli. Specifically, we sought to determine the involvement of the endogenous opioid peptide-mediated system as well as the role of the μ(1)-opioid receptor in antinociception organisation induced by acute sucrose intake. Nociception was assessed with the tail-flick test in rats (75, 150 and 250 g) of different ages acutely pre-treated with 500 μL of a sucrose solution (25, 50, 150 and 250 g/L) or tap water. Young and Adult rats (250 g) showed antinociception after treatment with 50 g/L (during 5 min) and 150 g/L and 250 g/L (during 20 min) sucrose solutions. Surprisingly, this antinociception was more consistent in mature adult rodents than in pups. To evaluate the role of opioid systems, mature adult rodents were pre-treated with different doses (0.25, 1 or 4 mg/kg) of the non-selective opioid receptor antagonist naloxone, the selective μ(1)-opioid receptor antagonist naloxonazine or vehicle followed by 250 g/L sucrose solution treatment. Sucrose-induced antinociception was reduced by pre-treatment with both naloxone and naloxonazine. The present findings suggest that sweet substance-induced hypo-analgesia is augmented by increasing sucrose concentrations in young and adult rodents. Acute oral sucrose treatment inhibits pain in laboratory animal by mediating endogenous opioid peptide and μ(1)-opioid receptor actions.
authors.affiliation: Laboratório de Neuroanatomia & Neuropsicobiologia, Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo, Av. dos Bandeirantes, 3900, 14049-900, Ribeirão Preto (SP), Brazil.
authors.forename: Renato Leonardo
authors.initials: RL
authors.lastname: de Freitas
authors.forename: João Marcus Lopes
authors.initials: JM
authors.lastname: Kübler
authors.forename: Daoud Hibraim
authors.initials: DH
authors.lastname: Elias-Filho
authors.forename: Norberto Cysne
authors.initials: NC
authors.lastname: Coimbra
mesh_terms: D000284:Administration, Oral; D000700:Analgesics / Q000008:administration & dosage*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D008297:Male; D018847:Opioid Peptides / Q000502:physiology*; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D017450:Receptors, Opioid, mu / Q000502:physiology*; D013395:Sucrose / Q000008:administration & dosage*; D013649:Taste
chemical_list: D000700:Analgesics; D018847:Opioid Peptides; D017450:Receptors, Opioid, mu; D013395:Sucrose