High pressure oxygenation in unanesthetized brain: mitochondrial activity, pyridinenucleotide redox state, and electrical activity

The effects of hyperbaric oxygenation (HPO) on mitochondrial activity, NADH oxidation-reduction state, and electrical activity were studied in the unanesthetized rat brain. Mitochondrial activity was measured in vitro after isolation of the mitochondria from brains exposed to HPO in vivo for various time intervals. The results showed that exposure of the brain to HPO in vivo decreased state 3 respiration of the mitochondria within 5-10 min of exposure. The level of respiration remained low until the final step of exposure. Despite this low respiration rate in vitro, the brain from which the mitochondria were isolated showed an oxidized state that, in comparison to the normoxic level of NADH, suggested a higher rate of respiration had occurred as a response to the convulsion appearing in vivo.