Figure 8. Cholesterol improves learning and memory in old rats.

• A The spatial abilities of 20M rats subjected to intra-ventricular infusion of control or cholesterol solution were evaluated in the Morris water maze. The animals were trained three times each day over 4 days, and the learning curves were plotted for the two groups. Average group distance (cm) to find the hidden platform across trials is shown, whereby cholesterol-treated rats (n = 9) outperformed their controls (n = 11) in the water maze on day 4 (repeated-measure ANOVA, F_1,2 = 7,707; P = 0.008), and significant differences were found in trial 11 (Bonferroni post hoc test, P = 0.019).
• B, C One day after acquisition of spatial learning, the strength of long-term spatial memory was evaluated in a probe trial without the platform. The percentage time spent in the quadrant of the pool that previously contained the platform (Q1) was significantly higher for cholesterol-treated animals compared to the rats that received the vehicle alone (two-sided t-test, P = 0.016), as shown in (B). Time spent in the target quadrant over the total time spent in the target and the opposite quadrant: Q1/(Q1 + Q3) is shown in (C). While vehicle-treated rats performed at chance level (0.5 represented by a dashed line), cholesterol-treated rats had a good spatial memory index (two-sided t-test P = 0.012). The results clearly show that cholesterol treatment improved spatial memory in old rats.