A high linoleate and a high α-linolenate diet induced changes in learning behavior of rats. Effects of a shift in diets and reversal of training stimuli

Rats fed from weaning on semi-purified diets supplemented either with linoleate-rich safflower oil (S) or α-linoleate-rich perilla oil (P) were mated. Half of the progeny were weaned to the original diet of the dams (SS and PP), the other two groups were shifted to diets enriched in the other fatty acid (SP and PS). Brightness- discrimination learning ability was tested daily for 30d beginning at 11 weeks of age, with a bright light as the positive stimulus. The learning performance was inferior in the group fed the safflower diet through two generations (SS) as compared with groups fed the perilla diet through two generations (PP) or for which the diets were shifted at weaning (PS and SP). The ducosahexaenote content of brain phospholipids was significantly less in the SS group compared with the three other groups. After 30d of the learning test, the effect of shifting the stimulus was tested for another 30d, this time using a dim light as the positive stimulus. The learning performance was superior in the PP group to the SS group throughout the latter 30 sessions, the difference being even more obvious than during the first 30d. These results indicate that the decrease in the discrimination-learning ability induced by α- linolenate deficiency is a relatively reversible process; both the docosahexaenoate content in brain and the learning performance were restored by supplementing α-linolenate after the weaning.