Morris water maze

The spatial learning and memory ability of rat was evaluated by Morris water maze (MWM, DMS-2, Beijing, China) on day 21 and day 35 after 2VO surgery, respectively. Morris water maze was used to test cognitive function [1,2]. The water maze used in our study was a flat black galvanized metal tank that was 210 cm in diameter and equipped with a platform 1-2 cm below the surface of the water. The rats were trained for 5 consecutive days, followed by the probe trial on day 6 with the original platform removed. The rats were trained four times per day (120 sec/trial) and were let down in four random places (N, W, SE, NW) in the pool. If the animals failed to locate the platform within 120 seconds, they were put on the platform and stayed for 20 seconds before the next swim trial. The latency was recorded as 120 seconds. If the animals reached the platform within 120 seconds, they were immediately removed from the platform. On day 6, a spatial probe trial was conducted with the original platform removed to evaluate memory retention. The animals were let down diagonally from the platform. The cumulative time spent in target quadrant where the platform was located was recorded during a period of 60s. The results were presented as the time spent (time percentage) in the target quadrant.