The Morris Water Maze Test

The Morris water maze (MWM) test was used to assess spatial learning and memory. Each mouse performed five acquisition trials (maximal swimming time 120 s; 5 s on the platform; 4 h inter-trial interval per day) over five consecutive days. The MWM test was performed before (2 days) and after (2, 4, and 7 days) surgery. Each mouse was placed in a circular pool (diameter 100 cm) filled with water (21–22°C) that was rendered opaque by addition of white paint. The mouse was trained to find a hidden platform (diameter 8 cm) submerged 1 cm below the water surface. Visual cues were placed on the four walls of the pool at 0.5 m distance from the center. All movements were video-tracked (NoldusEthoVision XT, Leesburg, VA, USA). We recorded swimming speeds, the times spent in the four quadrants, swim path lengths, and escape latencies. The mean escape latency time was the absolute escape latency and the ratio of this to the preoperative figure was the relative escape latency.