Brain glycogen depletion following prolong exercise in rats
Takashi
Matsui
Laboratory
of Exercise Biochemistry, University of Tsukuba Graduate School of
Comprehensive Human Sciences, Japan
Some brain loci utilize glucose as an
energy source during exercise. On the other hand, brain glycogen is
increasingly understood to be an important factor in brain energy metabolism.
However, it is uncertain whether glycogen is utilized as an energy source in
the brain during exercise. This is because brain glycogen is rapidly depleted
by activation of glycogenolysis enzymes under the hypoxic-ischemic conditions
that occur after animals are killed. Therefore, in our present study, by using
a high-energy focused microwave irradiation (MI) method which can momentarily inactivate
glycogenolysis enzymes, we tried to accurately measure the changes in brain
glycogen during exercise. Rats were subjected to running at 20 m/min for 2
hours. Nine brain loci were collected following MI fixation immediately after
cessation of exercise and were used for determination of glycogen. Glycogen
levels in the cortex, hippocampus, hypothalamus, cerebellum, and medulla
oblongata decreased more than 50 % with exercise. On the other hand, glycogen
levels in the septum, striatum, thalamus, and midbrain were not significantly
reduced by exercise. These results suggest that glycogen in some brain loci may
serve as an energy store during prolonged exercise.
Key words: Exercise, Brain, Glycogen