果蠅腦內蕈狀體的神經傳導參與嗅覺趨化行為

Chemotaxis behavior involves neurotransmissions from mushroom bodies in the Drosophila Brain

鄧景云(Ching-Yun Teng)

指導教授 ： 江安世

國立清華大學/生命科學院/生物科技研究所/碩士(2013年)

摘要

摘要
目前神經科學中最大的挑戰，來自於研究感覺訊號傳到腦中較高層級的腦區時，這些較高層級的腦區是如何處理同時進來的許多不同的訊號，以決定生物面對這些複雜訊號時的適當行為反應。在一般環境中，多數的味道都會影響果蠅做出迎趨或是逃避的反應，甚至同一種味道的濃烈多寡就會產生不同的喜歡或厭惡的反應。果蠅的嗅覺系統是由嗅覺感受神經細胞(olfactory receptor neurons)接收到氣味分子之後，將產生的訊號交由嗅覺投射細胞 (projection neurons)傳到更高層級的腦區-蕈狀體（mushroom bodies）及側角（lateral horn）。為了了解蕈狀體在訊號處理的過程中扮演的角色，我們阻斷蕈狀體不同部位的神經傳導後，給予果蠅不同濃度的MCH及OCT（兩種果蠅討厭的味道）。發現當我們在低濃度的MCH及OCT之下，阻斷蕈狀體的α’/β’ lobes神經傳導物質，會破壞果蠅正常的逃避行為 ; 但在高濃度時卻沒有觀察到此現象。另外，我們也發現當阻斷蕈狀體的α/β lobes神經傳導物質時，會破壞果蠅對蘋果醋正常的吸引行為。這此實驗發現果蠅腦內蕈狀體的不同區域分別參與嗅覺躲避和吸引的行為反應，其中α’/β’ lobes參與著果蠅嗅覺逃避行為的訊息傳遞，而α/β lobes則參與果蠅嗅覺吸引行為的訊息傳遞。

關鍵字

蕈狀體 ； 嗅覺 ； 趨化行為

並列摘要

Abstract
The greatest challenge for neuroscience at present is to address how sensory coding is represented from sensory input to the higher brain centers, where neural activity and information integration is computed in order to elicit appropriate behavior responses. In Drosophila, most odorants elicit either attraction or avoidance, depending on their concentration as well as their identity. Olfactory information is received from olfactory receptor neurons (ORNs) and then transferred to the two higher brain centers - mushroom bodies (MBs) and lateral horns (LHs) - via secondary olfactory neurons - projection neurons (PNs). To figure out the function of MBs in olfactory processing, we specifically disrupted neurotransmitter outputs from different lobes of the MBs and examined the resulting avoidance and attraction behavior after exposure to two different repellents - methyl cyclohexanol (MCH) and octanol (OCT) and one attraction odorant- apple cider vinegar (ACV). We found that neurotransmitter outputs from α’/β’ lobes in MBs are necessary for avoidance behavior at low concentrations of repellents but not at high concentrations. We also demonstrated that α/β lobes in MBs is necessary for attraction behavior. These findings suggested that the avoidance and attraction olfactory information may be separately processed in the different lobes of MBs in Drosophila brain.

並列關鍵字

mushroom bodies ； attraction behavior ； avoidance behavior ； chemotaxis behavior

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