title: A study of central opioid receptor involvement in nitrous oxide analgesia in mice.
abstract: This study was undertaken to assess the sensitivity of nitrous oxide (N2O) analgesia to antagonism by intrathecally (IT) and intracerebroventricularly (ICV) administered antagonists selective for kappa- and mu-opioid receptors. Male ICR mice were pretreated IT or ICV with the kappa antagonist nor-binaltorphimine (nor-BNI), 1 or 50 nmol, respectively, or distilled water (control), then exposed to N2O (50% or 75% in oxygen). Compared with IT control mice, IT nor-BNI-pretreated mice responded with significantly less analgesia. Compared with ICV control mice, ICV nor-BNI-pretreated mice also showed markedly reduced analgesic response. Other mice were pretreated IT or ICV with either the selective and irreversible mu antagonist beta-funaltrexamine (beta-FNA, 5.0 micrograms) or distilled water (control). When exposed to N2O 24 h later, beta-FNA-pretreated and control mice exhibited comparable analgesic responses. These preliminary results suggest that N2O analagesia in mice may involve spinal and supraspinal kappa-opioid receptors but not mu-opioid receptors.
authors.affiliation: Children's Hospital of Wisconsin, Milwaukee.
authors.forename: D C
authors.initials: DC
authors.lastname: Chen
authors.forename: R M
authors.initials: RM
authors.lastname: Quock
mesh_terms: D000698:Analgesia; D000818:Animals; D001667:Binding, Competitive; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D008297:Male; D051379:Mice; D009271:Naltrexone / Q000008:administration & dosage / Q000031:analogs & derivatives; D009609:Nitrous Oxide / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000187:drug effects*; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu
chemical_list: D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; C051843:binaltorphimine; D009271:Naltrexone; C024524:beta-funaltrexamine; D009609:Nitrous Oxide