SummaryThe effects of dietary docosahexaenoic acid (DHA, C22:6 n -3) connecting phospholipids on the learning ability and fatty acid composition of the brain were investigated in hypercholesterolemic mice. ICR mice were subjected to a very low level of n -3 fatty acids through two generations. At 4 wk of age, the F 1 generation, n -3 fatty acid deficient male mice were provided with an experimental diet containing four kinds of lipids (safflower oil: Saf, DHA connecting triacylglycerols: DHA-TG, DHA connecting phospholipids: DHA-PL, soybean phospholipids: Soy-PL) for 5 wk. Another group of ICR mice were obtained and fed a commercial diet (CE-2, CLEA Japan, Inc.) as a control. The learning and memory abilities of the mice were evaluated by the modified avoidance procedure. The learning and memory ability level was significantly higher in mice fed the DHA-PL diet than in those fed the Saf and Soy-PL diets, and was the same level as the control. The DHA levels of phosphatidylethanolamine in the brain were significantly higher in the mice fed the two types of DHA-containing diets than in those fed the Saf and Soy-PL diets and was not significantly different between DHA-TG and DHA-PL. The dimethylacetal levels in the brain were significantly higher in the mice fed the DHA-PL diet than in those fed the Saf and DHA-TG diets. These results suggest that the dietary DHA connecting phospholipids have the effect of improving memory learning, and may be related to the both the DHA and plasmalogen levels in the brain.

ABSTRACT. Using an elevated plus-maze test, we evaluated anxiety level in rats given ovary lipid extracted from Skipjack tuna (Katsuwonus pelamis; OLS). The percentage of open time was significantly higher in rats given OLS than in rats in the control group, but lower than in rats given diazepam (1.0 mg/kg body weight). Based on this fact and findings about other indicators, this study showed that OLS does not have as fast-acting and strong an anti-anxiety effect as diazepam but that continuous ingestion of OLS causes an antianxiety effect in animals. KEY WORDS: anxiety, elevated plus-maze test, ovary lipid.J. Vet. Med. Sci. 69(6): 633-636, 2007 Ovary lipid from Skipjack Tuna (Katsuwonus pelamis; OLS), extracted and purified using our patented method (JP Laid-Open No. 2004-2663, contains a large amount of docosahexaenoic acid (DHA) in the form of phospholipids such as phosphatidylcholine, phosphatidylethanolamine, and lysophosphatidylcholine. We hypothesized that if OLS ingestion relieves anxiety in companion animals, it could be useful in the treatment of problem behaviors. The elevated T-maze test is an excellent tool used for distinguishing an animal's underlying and intrinsic anxiety and/or fear from memorized behaviors [2,5,11,13,14]. Previously, we studied anxiety and/or fear using an elevated T-maze test with rats given OLS. We found that OLS shortened avoidance latency at the first trial, indicating that it has an effect against anxiety and/or fear [9]. In the present study, we evaluated the anti-anxiety effect of OLS using an elevated plus-maze test [1, 3, 4, 6-8, 12, 15], which is often used to determine anxiety level.In the previous study using an elevated T-maze test, rats were given OLS mixed as a lipid component in feed. As OLS is rich in n-3 fatty acids, the control feed was prepared to give the same energy percentage as n-3 fatty acids and the same n-6/n-3 ratio [9]. In the present study, rats were also given OLS mixed as a lipid component in feed. As this study evaluated anxiety level, however, the control group was given AIN93 and the OLS group was given AIN93, in which the lipid content was partly replaced with OLS. The animal raising period for the previous elevated T-maze test was 42 days. OLS ingestion for a shorter period decreased the rodent stress hormone corticosterone under acute stress [10]. Thus, the raising period was set at 28 days in the present study. Diazepam was used as a positive control. Observations were recorded during the first 5 min [7] (0-5 min) and then up to 15 min [8] (5-15 min) thereafter.The ovary was removed from the Skipjack tuna (Katsuwonus pelamis), washed with water, boiled, freeze-dried, powdered, and extracted with ethanol. The resultant extract was filtered and concentrated to obtain ovary lipid of Skipjack tuna (OLS).Four-week-old male Wistar rats (Japan SLC, Inc.) were used in the experiments. They were raised in an animal room maintained at a temperature of 23 ± 1°C, humidity of 55%, and a light/dark cycle of 12 hr (lighting 7:00-19:00, automatically...

In our previous experiments with rats, ovary lipid from Skipjack Tuna (Katsuwonus pelamis) (OLS) was shown to have a mitigating effect on anxiety and/or fear in elevated T-maze tests. This suggests that OLS has some effect on the central nervous system (CNS) of rats. Thus, we performed experiments to examine the status of CNS in rats given OLS. The effect of OLS on chronic stress was also examined at the same time. The feed for control rats used oil and fat that have the same energy percentages for n-6 and n-3 fatty acids and the same n-6/n-3 ratio as OLS. As a result, rats given OLS for 28 days had lower serotonin levels in various brain areas regardless of stress application, showing that OLS affected the serotonin nervous system. From this, it was inferred that the ability of OLS to mitigate anxiety and/or fear resulted from its action on CNS, especially the serotonin nervous system. Substances other than the essential fatty acids may have been responsible for the action of OLS on monoamines and the metabolites. The effect of OLS on CNS, especially the serotonin nervous system, suggests that OLS may suppress anxiety.