The Important Role of Lipids in Cognitive Impairment

Iii. Results

The hippocampus-dependent learning and memory of LPL-deficient mice were studied by performance in the water maze and step-down passive avoidance tests. During the training sessions (days 1 and 2) for the water maze test, LPL-deficient mice spent a significantly longer amount of time than WT mice to find the terminal escape platform. There were no differences in the number of entries into the non-exit arms on day 1 of training between the two genotypes. The number of no-exit arm entries by the LPL-deficient mice significantly increased on day 2 of training. From days 3 to 7, both the latency to escape the platform and the frequency of entries into the no-exit arms by the LPL-deficient mice were significantly increased compared with those by the WT mice. There was a significant correlation between the latency to escape the platform and the number of errors. No changes in swim speed were observed during the training period. Taken together, these observations suggest that the increase in latency to platform is most likely due to the impairment of navigational strategy in the LPL-deficient mice. We further used a step-down inhibitory avoidance task to study the role of LPL in learning and memory. A significant decrease in the latency to step-down was observed in the LPL-deficient mice during the training trial. Similarly, a shortened retention time was observed in the LPL-deficient mice.