阿茲海默症（AD）作為一種慢性神經退化性疾病，是目前造成老年癡呆的最主要病因之一。大量研究表明，Amyloid beta (Aβ)在其致病機轉中扮演了重要的角色。一些研究認為，Aβ的細胞毒性主要是由其多聚物造成的，但仍然無法確定是細胞外的還是細胞內的堆積才是造成毒性的最主要原因。Aβ會破壞AD病人腦中神經元的興奮﹣抑制平衡，加劇病變的發生。一些早期症狀通常和glutamatergic 神經元的功能異常同期發生，這些異常或許與 Aβ產生和沉積有關。GABA則是神经系统中重要的抑制性神经传导物质，对神经元的活性以及功能有重要作用。因此, 本篇研究利用果蠅為實驗材料，結合GAL4/UAS系統，將Aβ表現在glutamatergic和GABAergic神經元上以觀察其細胞毒性。通過改良的方法，我們利用6E10抗體成功在果蠅大腦內觀察到Aβ堆積的存在。Aβ表現於果蠅的glutamate neurons 或GABAergic neurons中時，我們觀察到在果蠅觸角葉外圍形成大量的堆積，并造成周圍神經元的減少。這一現象在glutamatergic和GABAergic 神經元中均有發生，結合近期研究的結果，我們推論Aβ通過形成大量的細胞外堆積對果蠅嗅覺的兩套平行抑制系統均會造成神經退化的影響，並且在GABAergic神經元上的影響要大於及較早與glutamatergic神經元。總的來說，本研究以直接證據證明了Aβ在果蠅腦中的存在，為將來更進一步研究其在AD發病機制中的作用提供更為有利的支持。

Alzheimer’s disease (AD) is the well-known and leading cause of dementia. Amyloid beta (Aβ), one of AD’s early onset pathological hallmarks, has been studied in many different aspects including in vitro and in vivo researches. Some of those studies revealed that the oligomer form rather than the fibrils of Aβ is the major cause of its cytotoxicity. We know little about how two kinds of deposition formed during aging: intracellular and extracellular depositions. Which is the major deposition leading to neuron dysfunction? Aβ can destroy the balance between neuron excitatory and inhibitory. Glutamatergic neuron is the classic excitatory neurons whose excitotoxicity usually come up with Aβ deposits and gamma-aminobutyric acid (GABA) is the classic inhibitory neurotransmitter, both are necessary for learning and memory. Here, we used the model organism Drosophila with the adequately established GAL4-UAS system to express Aβ in glutamatergic and GABAergic neurons to explore its toxic effects. By using general Aβ antibody, we identified the existence and deposits of Aβ, which have not been done in early studies. We found the neuron loss induced by Aβ and these Aβ deposits emerged at a very early stage. Deposits are earlier and largely found in/or around the antennal lobe, indicating that olfactory system, the major part for Drosophila to sense and establish memory is the most affected which is full of glutamatergic and GABAergic neurons. Together, this study provided a great, direct evidence of Aβ plague-like deposition existence in Drosophila AD model, which can be useful for better utilization of this powerful model organism.

Abstract I
摘要 II
Introduction 1
Alzheimer’s disease 1
Amyloid hypothesis 2
Glutamatergic neurons and AD 3
GABAergic neurons and AD 4
Drosophila model 5
Materials and Methods 7
Drosophila genetics and stocks 7
Immunohistochemistry and confocal images 7
Results 8
GAL4 lines expression pattern confirmed by GFP labeling 8
Aβ deposited in glutamatergic and GABAergic neuron 9
Aβ is intracellular in dopaminergic neuron but mostly extracellular in glutamatergic and GABAergic neuron 10
Aβ induced glutamatergic and GABAergic neuron loss 11
Characterization of Aβ distribution pattern in glutamatergic and GABAergic neurons 12
Discussion 13
Identification of Aβ in Drosophila 13
Drosophila antennal lobe to its olfactory memory may affect by Aβ 13
Intracellular VS extracellular 14
FIGURES 16
Figure 1. Expression patterns of glutamatergic and GABAergic neurons in Drosophila 16
Figure 2. Aβ expression in glutamatergic and GABAergic neurons 17
Figure 3. Intracellular and extracellular Aβ in different neuron types 18
Figure 4. Neuron loss induced by Aβ. 19
Figure 5. Characterization of Aβ deposition in Drosophila glutamatergic and GABAergic neurons. 21
Figure 6. Intracellular Aβ and extracellular Aβ analysis. 22
References 23

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