2.1. Rat model of focal cerebral ischemia/reperfusion

Male Sprague-Dawley (SD) rats (280–300 g) were purchased from SPF Biotechnology Co. (Beijing, China). Animal protocols for these studies were approved by the Institutional Animal Care and Use Committee of Xuanwu Hospital of Capital Medical University. The specific method we used to establish the right MCAO model in SD rats was described previously (Zhao et al., 2014). Briefly, rats were anesthetized with 2% isoflurane in N₂O:O₂ (70%:30%). MCAO was induced by the modified intraluminal filament method. The left common carotid artery, internal carotid artery, and external carotid artery branches were exposed by blunt dissection. A microscopic shear is then used to cut an incision in the external carotid artery stump, in which a 4–0 surgical nylon filament with a silicon-coated tip was inserted into the internal carotid artery approximately 18 mm beyond the carotid bifurcation, thereby occluding the origin of the middle cerebral artery. Rats were subjected to 90 min right MCAO followed by 6 or 24 h after reperfusion. Sham-operated rats underwent the same procedure without MCAO. A feedback temperature-controlled heating pad was used during and after surgery to maintain the rat’s body temperature at 37°C ± 0.5°C. Rats were housed in individual cages with free access to food and water (12-h light/dark cycles at 22°C ± 2°C).