The acute antinociceptive effect of hyperbaric oxygen is not accompanied by an increase in markers of oxidative stress

AimsExposure 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.Main methodsMale 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 11 min, 60 min, and 60 min daily for 2 days (120 min) or 60 min daily for 4 days (240 min), then assessed by analyzing the levels of two oxidative stress markers, MDA (malondialdehyde) and protein carbonyl in brain, spinal cord and lung.Key findingsOnly 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.SignificanceTreatment 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.