Posthypoxic treatment with MK-801 reduces hypoxic-ischemic damage in the neonatal rat

We evaluated the neuroprotective effect of MK-801, a noncompetitive, selective N-methyl-D-aspartate receptor antagonist, in a neonatal hypoxic-ischemic animal model. Seven-day-old rats underwent bilateral ligation of the carotid arteries followed by exposure to an 8% oxygen atmosphere for 1 hr. We sacrificed the animals 72 hrs later and assessed the hypoxic-ischemic brain damage histologically. MK-801 (10 mg/kg), administered IP 0.5 hr before the hypoxia, completely prevented hypoxic-ischemic infarction in cerebral cortex, while treatment immediately and 1 hr after the end of the hypoxia resulted in 76% and 52% reduction in the infarcted area, respectively. MK-801, given 0.5 hr before and immediately after the insult, reduced striatal damage and, given 0.5 hr before, attenuated neuronal necrosis in hippocampal regions. These results show that in neonates MK-801 is neuroprotective even when administered up to 1 hr after the end of a hypoxic-ischemic insult.