Vol. 91, Issue 3, 1193-1198, September 2001
Downregulation of nitric oxide in the brain of mice during
their hypoxic preconditioning
Guo-Wei
Lu and
Hong-Yan
Liu
Department of Neurobiology, Capital University of Medical Sciences,
Beijing 100054, China
An animal model of hypoxic
preconditioning was produced in mice by repeated exposure to
autohypoxic condition. The animals' tolerance times to hypoxia
were 1.7, 1.8, 2.1, and 2.3 times longer in runs 2,
3, 4, and 5, respectively, than that
in run 1, and their oxygen consumption and heart and
respiration rates were progressively and significantly slowed down
during the repetitive exposure to hypoxia. L-Arginine
concentration, nitric oxide (NO) synthase-positive cells, NO synthase
activity, and NO content in the whole brain and the subregions
telencephalon, diencephalon, and brain stem were significantly
increased during the first exposure and were, instead of continuing to
increase, significantly decreased in run 4 after the second
and third exposure. Tolerance times under the hypoxic condition were
significantly shortened and prolonged when preadministration of
L-arginine and its analog, respectively, was made. These
results indicate that NO in the brain is downregulated under condition
of hypoxic preconditioning and negatively involved in increased
tolerance to hypoxia.
L-arginine; nitric oxide synthase; N-nitro-L-arginine
