2.1. Animal Model

All experiments were approved by the Ethics Committee for Animal Care of Jinshan Hospital affiliated to Fudan University. A modified Rice–Vannucci model was used as previously described [27, 28]. The neonatal HI model was performed on Sprague-Dawley male rat pups (Slac Laboratory Animal Company, Shanghai, China) on postnatal day 3 (P3) via ligation of the left common carotid artery under 3% isoflurane anesthesia. Surgery time for each rat was controlled within 10 minutes. After recovery for 1 hour, these pups were placed in a hypoxia chamber at 37°C and subject to the gas mixer composed of 8% O₂ and 98% N₂ for 3.5 hours. Sham animals had the same operation to expose the common carotid artery without ligation and hypoxia. After surgery, the rat pups were returned to their home cage.