果蠅腦中橢圓體之麩胺酸受器對長期記憶之特殊重要性

在人類以及其他的許多種動物，記憶的固化往往會在不同時間顯現階段式的變化，而且都需要多個大腦區域的參與。在果蠅這個模式動物中，對於學習與記憶的研究已經證實了果蠅與哺乳類動物一樣，也可以形成各種不同時效的記憶。果蠅的嗅覺記憶可以區分成短期記憶，中期記憶，長期記憶以及抗昏迷記憶。由以往的研究結果已知果蠅腦中蕈狀體是在嗅覺關連性學習與記憶中不可缺少的腦內運算中心，因而推論記憶是在該處形成。然而本篇論文利用高解析度影像技術觀察，發現麩胺酸受器在果蠅腦中的橢圓體結構有大量的表現，之後利用基因轉殖技術表達果蠅麩胺酸受器的RNAi於特定的果蠅腦組織，進而發現若於橢圓體結構表達此RNAi，則破壞果蠅長期記憶的固化，但絲毫不影響中期記憶的產生。然而表現麩胺酸受器的RNAi於蕈狀體明顯抑制中期記憶的產生但不影響長期記憶。跟據此結果我們推論蕈狀體主要是負責中短期記憶的儲存。然而長期記憶則是儲存於橢圓體結構，而非蕈狀體結構。各種不同時效的記憶儲存都需要腦內的麩胺酸受器來控制。此研究對神經科學家了解大腦如何運作以及進行一連串複雜的學習記憶有重大的啟發。

關鍵字

果蠅；麩胺酸受器；長期記憶

並列摘要

In humans and all other animals tested, memory consolidation occurs through multiple temporal phases and usually involves more than one neuroanatomical brain region. Genetic dissection of Pavlovian olfactory learning in Drosophila also has revealed multiple memory phases. While emerging studies suggest roles for antennal lobes (ALs) and dorsal paired medial (DPM) neurons, the predominant view holds that the long-term memory (LTM) is consolidated only in the mushroom body (MB) neurons. In this study, I demonstrate an acute requirement of NMDARs for LTM consolidation outside the MB. Knocking down, with RNAi, dNR1 or dNR2 in cholinergic large-field neurons, the R4m subtype, of the ellipsoid body (EB) specifically disrupts LTM. Knockdown of NMDARs in MB disrupts the middle term memory while leaving LTM intact. These results strongly suggest an anatomical site outside of MB involved in LTM consolidation, for the first time, therefore imply the existence of distributed regions for olfactory memory formation in Drosophila brains. My results also mean that functionally independent memory traces exist at different anatomical sites during memory consolidation. Such evidences for a system-level memory consolidation in an invertebrate imply that the transfer of memory from one brain location to another during memory consolidation may be evolutionarily conserved, in spite of huge anatomical (circuit) differences between flies and mammals.

並列關鍵字

Drosophila ； NMDA receptor ； long-term memory

參考文獻

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果蠅腦中橢圓體之麩胺酸受器對長期記憶之特殊重要性

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