title: Naloxone-induced analgesia: involvement of kappa-opiate receptors.
abstract: Rats treated with an acute high dose (30 mg/kg) or 4 days with a lower dose (5 mg/kg) of naloxone or naltrexone show an analgesic response at the hot-plate test. This paradoxical analgesic effect of the two mu-opiate receptor antagonists is blocked by the kappa opiate receptor antagonist MR 1452, and is modulated by the kappa opiate receptor agonist U 50-488. Our results suggest that kappa opiate receptors are involved in naloxone-induced analgesia and are consistent with a high degree of plasticity of the opiatergic system.
authors.affiliation: Department of Pharmacology, School of Medicine, University of Milano, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Bianchi
authors.forename: A E
authors.initials: AE
authors.lastname: Panerai
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000698:Analgesia; D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D001575:Benzomorphans / Q000494:pharmacology; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D009271:Naltrexone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D017288:Pain Threshold / Q000187:drug effects; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000187:drug effects*; D017450:Receptors, Opioid, mu / Q000187:drug effects
chemical_list: D000700:Analgesics; D001575:Benzomorphans; D009292:Narcotic Antagonists; D011759:Pyrrolidines; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D009270:Naloxone; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; C029552:Mr 1452