At 1 to 7 days, the [DELTA][PSI]m of the ipsilateral cortex of the HIBD group was significantly lower than the normal control group without much difference between each other.
The change of [DELTA][PSI]m in the ipsilateral cortex from the normal control, HIBD and HIBD + HBO groups at each time-point is summarized in Figure 1.
The main findings of the present study were: [DELTA][PSI]m of the ipsilateral cortex of the HIBD group within 7 days after HI had a 'drop-recovery-secondary drop' fluctuation, while in the HBO-treated rat pups the [DELTA][PSI]m showed a 'drop-recovery-secondary drop-secondary recovery' change pattern.
We used the Rice-Vannucci HIBD rat model, which presents the advantage of allowing the ipsilateral hemisphere of the animal to be the internal control (10).
The main mechanism of HBO in HIBD might be the favorable influence in the binding of [O.sub.2] in mitochondrial redox enzyme systems, which helps to improve mitochondrial function (26), and to inhibit apoptosis (27).
This may explain the mechanism for the recovery of [DELTA][PSI]m in the ipsilateral cortex in the HIBD + HBO group.
2) The effect of HBO to HIBD regarding memory or cognitive development was not evaluated.
In conclusion, the timing and mechanisms of HBO protection in HIBD have only been partially elucidated.