Morris water maze test

The Morris water maze test, including the space navigation test for 4 days and spatial probe test for 1 day, was performed to evaluate the rat functions in spatial learning and memory. The apparatus was a black circular pool of 150 cm in diameter and 60 cm high and was filled with warm (20 ± 1 °C) water, with the water temperature kept at 20 ± 1 °C during the whole experiment. During the experiment, an object of reference was set up at a fixed location outside the water maze. The escape platform was 9 cm in diameter and 1.0 cm below the water surface. The space navigation test lasted 4 consecutive days, with four trials per day. If the rat failed to find the platform within 90 s, the latency time was recorded as 90 s, and the rat was gently guided to the platform by the experimenter. After the space navigation test, the spatial probe test was performed on the fifth day, and the rats were allowed to swim for 90 s. The time spent in the target quadrant and the frequency to cross the platform were recorded. The behavioral test was recorded by the same person who was blind to the rat group. The data for the behavioral tests were collected and analyzed using the JLBehv behavioral analysis software (Ji Liang Science and Technology Company Limited, Shanghai, China).