Functional Motifs Composed of Morphologically Homologous Neurons Repeated in the Hindbrain Segments
Functional Motifs Composed of Morphologically Homologous Neurons Repeated in the Hindbrain Segments
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DOI：
10.1523/jneurosci.4610-13.2014
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发表时间：
2014-02
期刊：
影响因子：
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通讯作者：
Daisuke Neki;H. Nakayama;Takashi Fujii;Haruko Matsui-Furusho;Y. Oda
中科院分区：
文献类型：
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作者：
Daisuke Neki;H. Nakayama;Takashi Fujii;Haruko Matsui-Furusho;Y. Oda
沿神经轴的节段组织是脊椎动物中枢神经系统的一个显著特征。在许多鱼类中，后脑部分含有有序排列的网状脊髓神经元（RSNs）。对金鱼和斑马鱼后脑的rsn进行了形态学鉴定。具有相似形态特征的rsn被称为片段同源，并在相邻片段中重复。然而，对片段同源物之间的功能关系知之甚少。在这里，我们研究了Mauthner细胞（m细胞）和r4 - r6中不同系列的同源rsn之间的电生理连接，Mauthner细胞是4节段（r4）中一对已知可触发快速逃逸行为的巨大rsn。成年金鱼的配对细胞内记录显示m细胞与rsn之间的单向连接。其连通性在形态学同源物上是相似的。除MiD2cm细胞外，单个m细胞尖峰在同侧背侧的rsn （MiD细胞）和对侧的兴奋性突触后去极化中产生ipsp。抑制电位和兴奋电位分别有效抑制或增强靶rsn的尖峰。与对MiD细胞的侧化效应相反，单个m细胞尖峰在位于腹侧的双侧rsn （MiV细胞）上引起同样强烈的去极化，并且去极化高到足以使MiV细胞破裂。因此，r4-r6中重复rsn的形态同源性与其m细胞的功能连接密切相关，表明在m细胞启动的逃逸过程中，每种功能连接都是一个功能基序。
Segmental organization along the neuraxis is a prominent feature of the CNS in vertebrates. In a wide range of fishes, hindbrain segments contain orderly arranged reticulospinal neurons (RSNs). Individual RSNs in goldfish and zebrafish hindbrain are morphologically identified. RSNs sharing similar morphological features are called segmental homologs and repeated in adjacent segments. However, little is known about functional relationships among segmental homologs. Here we investigated the electrophysiological connectivity between the Mauthner cell (M-cell), a pair of giant RSNs in segment 4 (r4) that are known to trigger fast escape behavior, and different series of homologous RSNs in r4–r6. Paired intracellular recordings in adult goldfish revealed unidirectional connections from the M-cell to RSNs. The connectivity was similar in morphological homologs. A single M-cell spike produced IPSPs in dorsally located RSNs (MiD cells) on the ipsilateral side and excitatory postsynaptic depolarization on the contralateral side, except for MiD2cm cells. The inhibitory or excitatory potentials effectively suppressed or enhanced target RSNs spiking, respectively. In contrast to the lateralized effects on MiD cells, single M-cell spiking elicited equally strong depolarizations on bilateral RSNs located ventrally (MiV cells), and the depolarization was high enough for MiV cells to burst. Therefore, the morphological homology of repeated RSNs in r4–r6 and their functional M-cell connectivity were closely correlated, suggesting that each functional connection works as a functional motif during the M-cell-initiated escape.