The Effect Of Repetitive Hyperbaric Oxygenation To The Mitochondrial Membrane Potential Of The Brain Cortical Cells After Hypoxic Ischemic Brain Damage In Neonatal Rats

Abstract Objectives:To observe the effect of repetitive application of hyperbaric oxygen (HBO) to the mitochondrial membrane potential (△Ψm) of the brain cortical cells after hypoxic-ischemic brain damage (HIBD) in neonatal rats.Methods:150seven-day-old Sprague-Dawley (SD) rats were randomly divided into3groups:normal control, HIBD and HIBD+HBO groups. Rice-Vannucci HIBD model was used for the latter two groups with the left carotid artery ligated. HIBD+HBO group were treated with HBO for1-7days after HI. Rat pups were further divided into1d,2d,3d,4d,5d,6d,7d groups (n=10in each group). Single cell suspension of cortex was prepared respectively when animals were euthanized by decapitation, and incubated with Rhodamine123, the bio-marker of△Ψm. The mean fluorescence level (MFL) of Rho123was detected by flow cytometry. And the ATm absolute values of left hemisphere in each group were recorded as well for statistical analysis.Results:(1) In normal group, the△Ψm was (4.66±0.80) MFL(2) In HIBD group, the△Ψm at each time point was significant less than those in normal group (P<0.05) with the lowest△Ψm (3.02±0.48) MFL at1d time point. After2d time point, the△Ψm mildly increased, but the△Ψm at2～7d time points were not different from each other.(3) In HIBD+HBO group, the△Ψm at each time point was significantly less than that in normal control group with the lowest△Ψm (2.32±0.77) MFL at1d time point. The△Ψm had a’decrease first, then increase’tendency. The△Ψm at1-4d time points (P<0.05) was significantly lower than that of control group (P<0.05), while the△Ψm at5-7d time points recovered to close to normal level (P>0.05) with the highest△Ψm (4.55±1.41) MFL at6d time point.(4) Between HIBD+HBO and HBO groups, the△Ψm of HIBD+HBO group at1-3d time point was significantly less than that in HIBD group (P<0.05). There was no significant difference between two groups at5d time point. The△Ψm of HIBD+HBO group at6-7d time point was significantly higher than that in HIBD group (P<0.05).Conclusions:HI may consistently cause mitochondrial dysfunction for a comparatively long period to the cerebral cortex in neonatal SD rats. HBO intervention does not improve the mitochondrial function at early stage after HIBD, but repetitive application of HBO may improve the mitochondrial function in the cerebral cortex of neonatal SD rats. Further research is needed for the HBO therapeutic window in HIBD.