Changes in Maze Behavior of Mice Occur after Sufficient Accumulation of Docosahexaenoic Acid in Brain

Abstract

The relationship between the time of intake of docosahexaenoic acid [DHA, 22:6(n-3)] and maze behavior in mice was studied. Male Crj:CD-1 mice (3 mo old) were fed a diet containing 2 g DHA-ethyl ester/100 g diet plus 3 g palm oil/100 g diet (DHA-EE group) or a diet containing 5 g palm oil/100 g diet (control group) 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 control and experimental diets. In each maze-learning test, 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 in each trial, all mice were killed and the fatty acid compositions of plasma and brain lipids were determined. There were no significant differences in the results of the maze-learning tests between mice fed the diets at 1 or 2 wk in any of the three trials. After 1 and 3 mo, the DHA-EE diet groups required less time (P < 0.05) to reach the maze exit and strayed into blind alleys fewer times (P< 0.05) than did the control diet groups during trial 3. Significantly greater DHA levels were observed in the plasma and brain total lipids of the mice fed the DHA-EE diet after 2 wk, compared with those fed the control diet (P < 0.05), which was compensated for by lower arachidonic acid [20:4 (n-6)] levels. There were no significant differences in brain DHA levels among mice fed the DHA-EE diet 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 were 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 time after the incorporation of DHA into the brain for improvement in learning ability to occur.