SYNAPTIC CIRCUITS INVOLVING AN INDIVIDUAL RETINOGENICULATE AXON IN THE CAT
SYNAPTIC CIRCUITS INVOLVING AN INDIVIDUAL RETINOGENICULATE AXON IN THE CAT
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DOI：
10.1002/cne.902590202
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发表时间：
1987-05-08
影响因子：
2.5
通讯作者：
SHERMAN, SM
中科院分区：
文献类型：
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作者：
HAMOS, JE;VANHORN, SC;SHERMAN, SM
为了描述单个视网膜X细胞轴突在外侧膝状核中的回路，我们对视束中的这样一个轴突进行了生理学表征，并在轴内给它注射了辣根过氧化物酶。随后，我们通过1200个连续切片重建未标记的突触后神经元，恢复轴突，并用电子显微镜技术观察其标记终末的突触分布。我们发现轴突S的输出具有显著的选择性，因为在终杆的有限部分的43个可用神经元中，只有4个从标记的终末接收突触。此外，这些突触在四个神经元上的分布，我们称之为细胞1到4，相对于接触相同细胞的其他类型终末的突触不同，包括来自未标记的视网膜终末的突触。对于细胞1和3，标记的终末分别提供49%和33%的视网膜突触，这些突触位于树突和附件上。因此，从注入的轴突到这些细胞的突触与来自其他视网膜轴突的突触整合在一起。对于细胞2，标记的终末提供100%的视网膜突触，但这些突触汇聚在树突附件簇上，在那里它们与汇聚的抑制输入整合在一起。最后，对于细胞4，标记的终末提供了不到2%的视网膜输入，而且这些终末位于远侧；我们认为这些突触是发育过程中发生的生理上不适当的错误连接的残留物。这项研究的发现支持哺乳动物中枢神经系统神经元回路的选择性的概念，也揭示了外侧膝状核神经元的一些不同的整合特性。
In order to describe the circuitry of a single retinal X-cell axon in the lateral geniculate nucleus, we physiologically characterized such an axon in the optic tract and injected it intra-axonally with horseradish peroxidase. Subsequently, we recovered the axon and employed electron microscopic techniques to examine the distribution of synapses from 18% of its labeled terminals by reconstructing the unlabeled postsynaptic neurons through a series of 1,200 consecutive thin sections. We found remarkable selectivity for the axon''s output, since only four of the 43 available neurons in a limited portion of the terminal arbor receive synapses from labeled terminals. Moreover, the distribution of these synapses on the four neurons, which we term cells 1 through 4, varies with respect to synapses from other classes of terminals that contact the same cells, including synapses from unlabeled retinal terminals. For cells 1 and 3, the labeled terminals provide 49% and 33%, respectively, of their retinal synapses, and these are located on both dendritic shafts and appendages. Synapses from the injected axon to these cells are thus integrated with those from other retinal axons. For cell 2, the labeled terminals provide 100% of its retinal synapses, but these synapses converge on clusters of dendritic appendages where they are integrated with convergent inhibitory inputs. Finally, for cell 4, the labeled terminals provide less than 2% of its retinal inputs, and these are distally located; we suggest that these synapses are remnants of physiologically inappropriate miswiring that occurs during development. The findings from this study support a concept of selectivity in neuronal circuitry in the mammalian central nervous system and also reveal some of the diverse integrative properties of neurons in the lateral geniculate nucleus.