Animal treatment
Two months old C57BL/6J male mice(20-25g) were purchased from Chongqing Medical University’s Laboratory Animal Center. All animal procedures and experiments complied with the approved guidelines and were approved by the Laboratory Animal Ethics Committee of Chongqing Medical University (Animal Certificate of Conformity: SYXK (Chong Qing) 2018-0003).The laboratory animals’rooms were ventilated regularly.The animals were housed in a temperature, humidity, and light-controlled room with free access to water and standard feed at the same time every day. 48 male mice were randomly divided into four groups, 12 mice/group. D-gal (120mg/kg/day) was administered subcutaneously into mice daily for 42 days in the D-gal group. The D-gal+ Rg1 group received the same treatment as the D-gal group, except for a 15th-day intraperitoneal injection of Rg1 (40mg/kg/day×28d) (Dong ZY et al.2017). In the Rg1 group, the same amount of normal saline was administered subcutaneously for 14 days, followed by an intraperitoneal injection of Rg1 (40mg/kg/day×28d) on the 15th day. In the Control group, an equal volume of normal saline was injected subcutaneously at the same time.
Morris water maze
Following the 42-day treatment, we used the Morris water maze test to assess the spatial learning and memory ability of mice(YangXY et al,2021;Wang P et al,2017). Place navigation test was performed once a day for 5 days. The mice faced the pool wall and took turns to enter the water from 4 water entry points, and the time they took to locate the platform within the 60s was recorded. If they did not find the platform for more than 60s, the latency was recorded as 60s, and the mouse was guided on the platform and allowed to stay for 10s. The spatial probe test was performed on the 6th day, where the invisible platform was removed, the mouse launched from a certain entry point, and the swimming track of the mouse within the 60s after entering the water was recorded. The latency period of the mouse’s escape, the number of times that the mouse crossed the position of the original platform and the original platform were calculated as a percentage of residence time in the quadrant.