Morris Water Maze
One week after reperfusion, the mice were trained to perform in the Morris water maze navigation task. A circular pool (1.2 m diameter and 50 cm depth) was filled with water (maintained at 23 ± 2°C). A 10-cm platform was placed 1.5 cm underneath the water surface (to hide its visibility) in one quadrant of the pool. The navigation task was performed in the present study as previously described (Jing et al., 2015). Briefly, rats were first adapted to swimming for 2 min the day before testing. Over the following four consecutive days, rats underwent learning trials to escape water by finding the invisible platform. The maximum time for each rat to swim in the pool was 60 s. If the animal did not find the platform within 60 s, the rat was gently guided to the platform and left on it for 15 s. Each rat underwent four trials at four starting positions in four quadrants each day with an interval of 15 s. The platform was removed on the fifth day, and the rats were allowed to navigate in the pool for 60 s. The escape latency to find the platform in the first 4 days and the duration of swimming in the platform quadrant at the fifth day were recorded. All trial information was collected automatically by a video camera linked to an animal behavioral recording system (Ethovison XT, Noldus Information Technology Co, Netherland).