Postischemic hyperthermia induced caspase-3 activation in the newborn rat brain after hypoxia-ischemia and exacerbated the brain damage.

The effects of postischemic hyperthermia were investigated in the newborn rat brain after hypoxia-ischemia (HI). Seven-day-old rats were subjected to left carotid artery ligation followed by 8% oxygen for 30 min, and divided into a hyperthermia group (rectal temperature at 39 degrees C for 6 h) and a normothermia group. Hyperthermia resulted in an approximately 5-fold increase in activated caspase-3 24 h after HI when compared with the normothermia group, and gross loss of brain tissue was observed only in the hyperthermia group at 7 and 30 days after HI. Our results show that postischemic hyperthermia exacerbates HI injury in immature brains, and that the mechanism is strongly associated with activation of an apoptotic pathway.