Abstract: Objective To explore the effect of mild to moderate hypothermia on the expressions of apoptosis-related genes in the
brain tissue of rats after cardiopulmonary resuscitation (CPR). Methods CPR models were established by asphyxia in 15 male
SD rats, which were randomized equally into normal temperature group, 34 ℃ hypothermia group and 32 ℃ hypothermia
group. The brain tissues of the rats were obtained after treatment for 12 h to observe the pathological changes. The expression
of caspase-3 in cerebral cortex neurons was determined with immunohistochemistry, and the expressions of Bcl-2 and Bax
were detected by Western blotting. Results Compared with normal temperature group, the two hypothermia groups
(especially 32 ℃ group) showed significantly decreased expression of caspase-3 in the cortical neurons (P<0.05). Bcl-2 protein
expression was significantly increased in the hypothermia groups, especially in 32 ℃ hypothermia group (P<0.05). There was
no significant difference in Bax protein expression among the 3 groups. Conclusion Mild hypothermia can relieve brain injury
by down-regulating caspase-3 expression and up-regulating Bcl-2 protein expression to inhibit apoptosis of the brain
neurons. Hypothermia at 32 ℃ offers better protection of the brain tissue than hypothermia at 34 ℃.