Effect of intake period of docosahexaenoic acid on maze‐learning ability in mice

Abstract

Male mice (3 mo old) were fed a diet containing 2% docosahexaenoic acid (DHA) plus 3% palm oil or a diet containing 5% palm oil for different periods of time. Maze-learning ability was assessed at 1 and 2 wk and 1 and 3 mo after the start of the experiment. The time required to reach the maze exit and the number of times that a mouse strayed into blind alleys in the maze were measured in three trials, one every 4 d. After the last learning test, all mice were killed and the fatty acid compositions of plasma and brain were determined. There were no significant differences in the maze-learning tests between mice fed the diets at 1 and 2 wk in any of the three trials. After 1 and 3 month, the DHA diet group required less (p<0.05) time to reach the maze exit and strayed into blind alleys (p<0.05) fewer times than the palm oil diet group. Significantly greater DHA levels were observed in the plasma and brain lipids of the mice fed the DHA diet after 2 wk, compared to those fed the palm oil diet (p<0.05), which was compensated for by lower arachidonic acid levels. There were no significant differences in brain DHA levels among mice fed the DHA for 2 wk, 1 mo, or 3 mo. Improved maze-learning ability after DHA intake was evident at 1 mo after the start of feeding and was maintained up to 3 mo, whereas the increased DHA levels in brain were apparent after feeding for just 2 wk. These results suggest that it may take some time after the incorporation of DHA in the brain to develop learning ability in mice.