Morris Water Maze Test

Spatial learning and memory performance of mice was evaluated by the Morris water maze test. The Morris water maze protocol has been described in detail in Morris’s previous report (Morris, 1984). In brief, the mice were placed in opaque water of a circular swimming pool and trained to find a platform hidden below the water surface in target quadrants according to the spatial cues in the experimental room. During the training to find the hidden platform, the mice were allowed to swim for a maximum of 60 s. One block of four trials per day (1 min swimming time, inter-trial interval of 40 min) was performed for five consecutive days. On the 6th day, mice were given a 60-s retention probe test during which the platform was removed from the pool. Data were collected using a ceiling-mounted video camera, and analysis by MobileDatum software (RD1101-MWM-G, MobileDatum, Shanghai, China). All Morris water maze tests were performed between 1 AM and 5 AM, and the water temperature is maintained at 20 ± 2°C.