title: The acute antinociceptive effect of hyperbaric oxygen is not accompanied by an increase in markers of oxidative stress.
abstract: OBJECTIVE
  Exposure to hyperbaric oxygen (HBO2) causes an antinociceptive response in mice. However, breathing oxygen (O2) at an elevated pressure can potentially cause oxygen toxicity. The aim of this study was to identify the determinants of HBO2 antinociception and the toxicity profile of HBO2.
  
  
  METHODS
  Male NIH Swiss mice were assessed for acute antinociceptive responsiveness under room air or 100% O2 at 1.0 or 3.5 atmospheres absolute (ATA), using the acetic acid-induced abdominal constriction test. For the oxygen toxicity test, mice were exposed to 3.5 ATA oxygen for 11min, 60min, and 60min daily for 2days (120min) or 60min daily for 4days (240min), then assessed by analyzing the levels of two oxidative stress markers, MDA (malondialdehyde) and protein carbonyl in brain, spinal cord and lung.
  
  
  RESULTS
  Only the combination of 100% O2 and 3.5 ATA caused significant antinociception. The antinociceptive effect of 100% O2 was pressure-dependent up to 3.5 ATA. In the oxygen toxicity test, mice exposed to HBO2 for different time intervals had levels of brain, spinal cord and lung MDA and protein carbonyl that were comparable to that of control animals exposed to room air.
  
  
  CONCLUSIONS
  Treatment with 100% O2 evokes a pressure-dependent antinociceptive effect. Since there was no significant increase in levels of the oxidative stress markers in the tested tissues, it is concluded that HBO2 at 3.5 ATA produces antinociception in the absence of oxidative stress in mice.
authors.affiliation: Department of Diving Medicine, Second Military Medical University, Shanghai, China; Department of Psychology, Washington State University, Pullman, WA 99164, USA.
authors.forename: Shulin
authors.initials: S
authors.lastname: Liu
authors.affiliation: Department of Physiology and Pharmacology, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA 95211, USA.
authors.forename: Donald Y
authors.initials: DY
authors.lastname: Shirachi
authors.affiliation: Department of Psychology, Washington State University, Pullman, WA 99164, USA; Translational Addiction Research Center, Washington State University, Pullman, WA 99164, USA. Electronic address: quockr@wsu.edu.
authors.forename: Raymond M
authors.initials: RM
authors.lastname: Quock
mesh_terms: D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D015415:Biomarkers / Q000032:analysis*; D001923:Brain Chemistry / Q000187:drug effects; D006931:Hyperbaric Oxygenation; D008168:Lung / Q000737:chemistry; D008297:Male; D008315:Malondialdehyde / Q000032:analysis; D051379:Mice; D018384:Oxidative Stress / Q000187:drug effects*; D010100:Oxygen / Q000494:pharmacology*; D050050:Protein Carbonylation / Q000187:drug effects; D013116:Spinal Cord / Q000737:chemistry
chemical_list: D000700:Analgesics; D015415:Biomarkers; D008315:Malondialdehyde; D010100:Oxygen
keywords: Antinociception; Hyperbaric oxygen; Malondialdehyde; Oxidative stress; Protein carbonyl