Department of Psychology and Neuroscience, Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2.
J Comp Neurol. 2012 Jul 1;520(10):2185-201. doi: 10.1002/cne.23037.
To investigate how sensory information is processed, transformed, and stored within an olfactory system, we examined the anatomy of the input region, the calyx, of the mushroom bodies of Drosophila melanogaster. These paired structures are important for various behaviors, including olfactory learning and memory. Cells in the input neuropil, the calyx, are organized into an array of microglomeruli each comprising the large synaptic bouton of a projection neuron (PN) from the antennal lobe surrounded by tiny postsynaptic neurites from intrinsic Kenyon cells. Extrinsic neurons of the mushroom body also contribute to the organization of microglomeruli. We employed a combination of genetic reporters to identify single cells in the Drosophila calyx by light microscopy and compared these with cell shapes, synapses, and circuits derived from serial-section electron microscopy. We identified three morphological types of PN boutons, unilobed, clustered, and elongated; defined three ultrastructural types, with clear- or dense-core vesicles and those with a dark cytoplasm having both; reconstructed diverse dendritic specializations of Kenyon cells; and identified Kenyon cell presynaptic sites upon extrinsic neurons. We also report new features of calyx synaptic organization, in particular extensive serial synapses that link calycal extrinsic neurons into a local network, and the numerical proportions of synaptic contacts between calycal neurons. All PN bouton types had more ribbon than nonribbon synapses, dark boutons particularly so, and ribbon synapses were larger and with more postsynaptic elements (2-14) than nonribbon (1-10). The numbers of elements were in direct proportion to presynaptic membrane area. Extrinsic neurons exclusively had ribbon synapses.
为了研究感觉信息在嗅觉系统中是如何被处理、转化和存储的，我们研究了果蝇蘑菇体输入区域（腔球）的解剖结构。这些成对的结构对各种行为很重要，包括嗅觉学习和记忆。输入神经胶质中的细胞，腔球，组织成一系列微结，每个微结由来自触角叶的投射神经元（PN）的大突触末梢组成，周围是来自内在的 Kenyon 细胞的微小突触后神经突。蘑菇体的外在神经元也有助于微结的组织。我们采用了遗传报告基因的组合，通过光学显微镜来识别果蝇腔球中的单个细胞，并将这些与从连续切片电子显微镜获得的细胞形状、突触和电路进行比较。我们确定了三种形态类型的 PN 末梢：单叶、聚类和伸长；定义了三种超微结构类型，具有清晰或致密核心囊泡，以及具有暗细胞质的两者都有；重建了 Kenyon 细胞的各种树突特化；并识别了外在神经元上的 Kenyon 细胞突触前位点。我们还报告了腔球突触组织的新特征，特别是将腔球外在神经元连接成局部网络的广泛串联突触，以及腔球神经元之间的突触接触的数量比例。所有 PN 末梢类型都有比非带状突触更多的带状突触，暗末梢尤其如此，而带状突触比非带状突触（1-10）更大，具有更多的突触后元件（2-14）。元件的数量与突触前膜面积成正比。外在神经元仅具有带状突触。
