Long-term neuroprotective effects of carbon dioxide on neonatal rat hypoxic-ischemic brain injury: An experimental study of skilled motor tasks

This study was undertaken to investigate the long-term effect of hypercapnia on neonatal hypoxic-ischemic brain injury, we tested its effect in a neonatal rat hypoxia-ischemia model. The rats were subjected to unilateral carotid artery ligation and exposure to 8% oxygen for 30 minutes. Six percent carbon dioxide was administered to the neonatal rats during unilateral hypoxia-ischemia, and the motor function and neurologic outcomes were determined 3 months later. Significant motor functional improvement was observed in the hypercapnic animals, as judged by the Montoya staircase test. The unilateral brain injury was significantly ameliorated in the hypercapnic animals, and this amelioration was well correlated with the motor functional performance. Cerebral blood flow during hypoxia-ischemia, monitored by laser Doppler flowmetry, was better preserved in the hypercapnic animals. Our results suggest that mild hypercapnia during hypoxia-ischemia may provide long-lasting motor functional as well as neurologic protection for immature brains, possibly by increasing cerebral blood flow during hypoxia.