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Influence of age in different brain regions without
treatment (EGb-/hypoxia-)
Studies of some markers of oxidative stress in several
organs of Wistar rats (6 and 22-25 months-old) have
shown that with respect to the liver, heart, and kidneys,
the aging brain is particularly susceptible to oxidative
damage, proved by the highest MDA content and the
lowest SOD activity and GSH content (16). We found
age to be an independent variable and a highly significant
predictor of MDA content in the temporal cortex,
the brainstem, and the cerebellum in rats (Figs. 2, 3).
The temporal cortex is a particularly sensitive area reacting
to environmental stress with increased motor
and sensory activity and elevated ROS production.
Findings of higher MDA and lipid peroxidation in the aging
brain are consistent with results reported in the literature
and can be explained by a higher generation of
free radicals with aging (15, 17-19). Contrary to findings
by some investigators who described a decrease in
SOD and GSH in most areas of the brain, we found an
elevation in SOD activity in the temporal cortex and in
the brainstem and in GSH content in the brainstem
and in the cerebellum of the old brain compared to
the young one (Figs. 2, 3). The explanation behind
these partly contradictory results could be that, contrary
to investigators who were concerned with protein mg tissue
wet weight, neglecting partly significant changes in
protein and water content in different brain areas during
aging, DNA was used in our study as a relation parameter
(Fig. 1) (14).
Our results then seem to demonstrate that the old
brain exhibits a high degree of peroxidation, but also a
certain amount of adaptation, proved by elevated antioxidative
factors to the increased chronic oxidative
stress to which it is exposed during the course of life.
This is in agreement with the results of Martinez-Romero
et al. (20), who observed a higher Mn- and Cu/ZnSOD
and Se-dependent GPX activity in the cerebral cortex
of old Wistar rats. Those Authors hypothesized
that increased ROS production has a preconditioning effect
following transient exposure to hypoxia, also
demonstrated in the old gerbil brain and in experiments
with primary cell cultures of cortical neurons
(21, 22).