果蠅通過嗅覺經由帕夫洛夫的古典制約式學習，可產生兩種不同的中期記憶：昏迷敏感性記憶（ASM）與抗昏迷記憶（ARM）。果蠅的昏迷敏感性記憶據信與一種神經胜肽－Amnesiac 有關，此神經胜肽被證實存在於果蠅腦中的於DPM神經元。而抗昏迷記憶的形成則被證實與果蠅腦中radish 基因有關。本實驗證明了當我們利用藥物來控制果蠅腦中血清素的含量時，促進血清素（serotonin）的含量會促進抗昏迷記憶的形成，反之抑制血清素的含量則會抑制抗昏迷記憶的形成。而在Amnesiac 突變株中，抑制血清素的含量會進一步降低抑制抗昏迷記憶的形成，此現象在radish突變株中並不會發生。這一點以證明radish與血清素作用於形成抗昏迷記憶的同一路徑上。我們更提出了三點證據證明了控制抗昏迷記憶形成的血清素，是由果蠅腦中的DPM神經元所釋放並由蕈狀體來接收此訊號：（1）免疫染色的結果證實DPM神經元含有血清素；（2）藉由降低DPM神經元中血清素的含量可以降低抗昏迷記憶的形成；（3）降低血清素接受體1A在蕈狀體alpha/beta腦葉（lobe）的表現量，亦可降低抗昏迷記憶的形成。因此，本實驗證實DPM神經元除了可經由釋放Amnesiac神經胜肽而促進抗昏迷記憶的形成，同時亦可釋放血清素以促進抗昏迷記憶的形成。

Pavlovian olfactory learning in Drosophila produces two genetically distinct forms of intermediate-term memories: anesthesia-sensitive memory (ASM), which requires the amnesiac gene, and anesthesia-resistant memory (ARM), which requires the radish gene. Here, we report that ARM is specifically enhanced or inhibited in flies with elevated or reduced serotonin (5HT) levels, respectively. The requirement for 5HT was additive with the memory defect of the amnesiac mutation but was occluded by the radish mutation. This suggests that 5HT and RADISH protein act on the same pathway for ARM formation. Three supporting lines of evidence indicate that ARM formation requires 5HT released from only two dorsal paired medial (DPM) neurons onto the mushroom bodies (MBs), the olfactory learning and memory center in Drosophila. (i) DPM neurons were 5HT-antibody immunopositive. (ii) Temporal inhibition of 5HT synthesis or release from DPM neurons, but not other serotonergic neurons, impaired ARM formation. (iii) Knocking down the expression of d5HT1A serotonin receptors in alpha/beta MB neurons, which are innervated by DPM neurons, inhibited ARM formation. Thus, in addition to the AMNESIAC peptide required for ASM formation, the two DPM neurons also release 5HT acting onto MB neurons for ARM formation.

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