2.7. Morris water maze (MWM)

The MWM was used to assess spatial learning and memory. The MWM consisted of a black circular pool (140 cm wide, 45 cm high) filled with water and surrounded by visual cues on the walls observable to the rats. Water temperature was set between 21°C and 23°C. A platform, either visible or submerged (15 cm wide and 35 cm height) was embedded 1.5 cm above or below the water surface. All the experiments were done between 8:00 a.m. and 12:00 p.m. Each rat was examined in three blocks of trials, and each block consisted of four trials begun from various locations in the MWM. The inter‐block interval was at least 30 min for each rat. Rats were placed in one of the quadrants of the water pool with their face directed toward the pool wall. The location of the platform did not change in the acquisition trial. Rats were monitored for 60 s during which the platform was found. When found, a 20–30 s break was given to the rat on the platform. The rat was returned to its cage, and again, after 20–30 s, the rat was placed into the water. The time spent and distance moved by the rats to find the platform were recorded by the software. To evaluate the spatial memory of the rats, a single probe trial was accomplished 2 hr after the last block of trials. In the probe trial, the platform was extracted from the tank and rats were permitted to swim for 60 s in the tank. Distance moved and time spent in the target quadrant were recorded for each rat as an index of spatial memory retention (Aghaei et al., 2015).