The influence of orally administered docosahexaenoic acid on cognitive ability in aged mice.

The purpose of this study was to investigate whether or not the role of docosahexaenoic acid (DHA) supplementation on cognitive capability was related with brain-derived neurotrophic factor (BDNF), nitric oxide (NO) and dopamine (DA) in aged mice. Kunming-line mice were treated with 50 and 100 mg/kg/day of DHA via oral gavage for seven successive weeks. The cognitive ability of mice was assessed by step-through and passageway water maze tests. The levels of NO in hippocampus and striatum tissues were assessed by spectrophotometric method. The levels of DA in hippocampus and striatum tissues were assessed by high-performance liquid chromatography with electrochemical detection. The protein levels of BDNF in hippocampus tissue were assessed by Western blotting. The results showed that the cognitive capability of mice was significantly different between the DHA-treated groups and the control group; the protein level of BDNF was significantly increased in the hippocampus; the levels of NO and DA were significantly increased in hippocampus and striatum tissues. In conclusion, during aging, DHA supplementation can improve the cognitive function in mice and can increase the protein level of BDNF in hippocampus tissue and the levels of NO and DA in hippocampus and striatum tissues. Taken together, our results suggest that DHA supplementation could improve the cognitive dysfunction due to aging, to some extent, and it may have a relationship with increasing the protein level of BDNF and the level of NO and DA.