探討海馬迴二十二碳六烯酸含量與空間學習記憶能力之相關性

Abstract

阿茲海默氏病（Alzheimer's disease）患者有短期記憶快速流失和海馬迴(hippocampus)二十二碳六烯酸(Docosahexaenoic acid, DHA, 22:6 n-3)含量減低等現象，而二十二碳六烯酸對神經正常功能的維持扮演重要的角色。本論文主要探討海馬迴中DHA含量與空間學習記憶能力的相關性。利用在不同生命時程餵給缺乏ω3脂肪酸的葵花油飼料或補充富含ω3脂肪酸的魚油的方式，創造出海馬迴DHA含量不同的雄性SD鼠。利用Morris水迷宮(Morris water maze)測量動物的空間學習記憶能力，並以氣相層析儀進行脂肪酸分析，量測其海馬迴、嗅球(olfactory bulb)、大腦額葉皮質（frontal lobe）、小腦（cerebellum）四腦區和紅血球(erythrocyte)組織中DHA含量。結果發現：（1）海馬迴的DHA含量正相關於空間學習記憶能力；（2）缺乏DHA的海馬迴、嗅球、大腦額葉皮質和小腦，在補充富含DHA的魚油80天後，分別回復至90%、96%、64%和73%，其中又以具學習與記憶功能的海馬迴和嗅球回復程度最佳；（3）紅血球組織(erythrocyte)中DHA所佔比例和海馬迴DHA含量有相關性，可作為檢測海馬迴DHA含量之指標。總結：海馬迴DHA缺乏時，可藉由在日常飲食中補充魚油攝取，回復其DHA含量，並增進空間記憶能力。

Background – Alzheimer’s disease is a progressing neurodegenerative disease characterized in short-term memory loss and associated with low docosahexaenoic acid (DHA, 22:6w3) in the hippocampus. Aim – It is hypothesized that hippocampal DHA level could be manipulated by diets and associated with spatial learning memory performance studied by Morris’s water maze. Design – Male rats was fed sunflower oil as ω3 deficient diet during brain development supplemented with or without fish oil to create various hippocampal DHA level. The animals at age of 100 days old performed the Morris water maze for learning ability and memory consolidation. Outcomes – The hippocampal DHA level is created from 15% down to 5% of total fatty acid composition. The learning memory and memory retention is significant better in adult animals containing higher hippocampal DHA level compared with the reduced hippocampal DHA level. Compared to controls, the deficiency of DHA in hippocampus, olfactory bulb, frontal cortex and cerebellum can be recovery back to 91, 96, 64, 73%, respectively. Conclusions – The hippocampal DHA level can be manipulated by diets, and be recovered back to normal from reduced DHA level in animals supplemented with fish oil. The learning memory performance is associated with hippocampal DHA level, and erythrocyte DHA level can be an index of hippocampal DHA level.