Hyperbaric oxygen preconditioning protects rats against CNS oxygen toxicity.

Area of Science:

• Neuroscience
• Hyperbaric Medicine
• Toxicology

Background:

• Central nervous system oxygen toxicity (CNS-OT) is a risk associated with hyperbaric oxygen (HBO) exposure.
• Preconditioning strategies are explored to mitigate adverse effects of HBO.
• The protective mechanisms of non-convulsive HBO preconditioning against CNS-OT are not fully understood.

Purpose of the Study:

• To investigate if repeated non-convulsive hyperbaric oxygen (HBO) exposure can protect against central nervous system oxygen toxicity (CNS-OT).
• To evaluate the impact of HBO preconditioning on antioxidant enzyme activity and nitrotyrosine levels in rat brain tissues.
• To elucidate the biochemical pathways involved in HBO-induced neuroprotection.

Main Methods:

• Four groups of rats were utilized, including control and preconditioned groups.
• Preconditioning involved exposure to non-convulsive HBO (202 kPa) three times over six days.
• CNS-OT was induced by exposure to convulsive HBO (608 kPa), with latency measured; hippocampal and cortical tissues were analyzed for enzymatic and nitrotyrosine levels.

Main Results:

• HBO preconditioning significantly increased latency to CNS-OT from 12.8 to 22.4 minutes.
• In the hippocampus, preconditioned rats showed decreased glutathione reductase and glucose-6-phosphate dehydrogenase activity, but increased glutathione peroxidase activity.
• Significantly lower nitrotyrosine levels and increased glutathione S-transferase and glutathione peroxidase activity were observed in the hippocampus and cortex of preconditioned rats.

Conclusions:

• Repeated non-convulsive hyperbaric oxygen (HBO) exposure confers significant protection against central nervous system oxygen toxicity (CNS-OT).
• The protective effects are mediated by alterations in the enzymatic activity of the brain's antioxidant system.
• Reduced peroxynitrite levels, particularly in the hippocampus, contribute to the observed neuroprotection following HBO preconditioning.