Figure 1. Metformin improved spatial learning and memory of older mice in the Morris water maze test. (A) Escape latency of 10–12-month mice treated with metformin (Met) (n = 9) was significantly shorter compared with the control group (Ctrl) (n = 11). (B) Probe tests conducted 24 h after the acquisition phase indicated that the first time-to-platform of 10–12-month-old mice treated with metformin was shorter than the control group. (C) No difference in swim speed was observed between control and metformin-treated groups. (D) Mean escape latency during 5 training days in 20-month-old mice treated with different doses of metformin. (E) Probe tests conducted after 24 h of the acquisition phase indicated that first time-to-platform was shorter in 20-month-old mice treated with higher doses of metformin than the control group. (F) No difference in swim speeds were observed between control and metformin-treated groups. (Number of mice in control group n=5, in 0.5mg/kg group n=6, in 5mg/kg group n=6, in 15mg/kg group n=5). The overall significance between two groups was determined by Student’s t-test, among three group was determined by one-way ANOVA. * p < 0.05, ** p < 0.01, *** p < 0.001, ns, not significant.