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研究发现驱动感觉丘脑抑制的回路
2020-07-24 17:14

美国布朗大学Scott J. Cruikshank研究组取得最新进展。他们发现两个动态不同的回路驱动感觉丘脑抑制。这一研究成果于2020年7月22日发表在《自然》杂志上。

他们通过小鼠TRN的体感和视觉回路进行研究。在体感TRN中,他们观察到两组遗传上定义的神经元,它们在位置上是分离的并且在生理上是不同的,并且通过动态发散的突触,相互独立地连接着丘脑皮层核。表达Calbindin的细胞(位于中央核心)与腹侧后核(主要的体感丘脑皮质中继器)相连。相比之下,生长激素抑制素表达细胞(位于TRN的周围边缘)与后丘脑内侧核突触相连,后者是一个高层结构,既携带自上而下又自下而上的信息。

这两个TRN单元组以途径特定的方式处理其输入。从腹后核到中央TRN细胞的突触传递快速的兴奋性电流,该电流在重复性活动期间会严重降低,从而驱动相态峰值输出。从丘脑后内侧核到边缘TRN细胞的突触激活的速度较慢,抑制兴奋电流的程度较低,从而驱动了更持久的峰值。TRN细胞类型的内在生理学差异(包括依赖状态的爆发)有助于这些输出动态。

因此,这两个体感TRN子回路的处理专业化似乎已针对它们所携带的信号进行了调整——将主要的中央子电路调整为离散的感觉事件,将更高阶的边缘子电路调整为从多个源集成的时间分布信号。视觉TRN子回路的结构和功能与体感TRN的电路和结构极为相似。这些结果提供了对TRN神经元子网如何差异处理丘脑信息类别的见解。

据悉,到达新皮质的大多数感觉信息通过丘脑传递,在丘脑中发生相当大的转变。转换的一种方式涉及,将数据携带到皮层的兴奋性丘脑皮质神经元,与调节这些数据流的丘脑网状核(TRN)的抑制性神经元之间的相互作用。尽管人们早已认识到TRN的重要性,但对其细胞类型、组织和功能特性的了解却落后于对它们所控制的丘脑皮质系统。

附:英文原文

Title: Two dynamically distinct circuits drive inhibition in the sensory thalamus

Author: Rosa I. Martinez-Garcia, Bettina Voelcker, Julia B. Zaltsman, Saundra L. Patrick, Tanya R. Stevens, Barry W. Connors, Scott J. Cruikshank

Issue&Volume: 2020-07-22

Abstract: Most sensory information destined for the neocortex is relayed through the thalamus, where considerable transformation occurs1,2. One means of transformation involves interactions between excitatory thalamocortical neurons that carry data to the cortex and inhibitory neurons of the thalamic reticular nucleus (TRN) that regulate the flow of those data3,4,5,6. Although the importance of the TRN has long been recognised7,8,9, understanding of its cell types, their organization and their functional properties has lagged behind that of the thalamocortical systems they control. Here we address this by investigating the somatosensory and visual circuits of the TRN in mice. In the somatosensory TRN we observed two groups of genetically defined neurons that are topographically segregated and physiologically distinct, and that connect reciprocally with independent thalamocortical nuclei through dynamically divergent synapses. Calbindin-expressing cells—located in the central core—connect with the ventral posterior nucleus, the primary somatosensory thalamocortical relay. By contrast, somatostatin-expressing cells—which reside along the surrounding edges of the TRN—synapse with the posterior medial thalamic nucleus, a higher-order structure that carries both top-down and bottom-up information10,11,12. The two TRN cell groups process their inputs in pathway-specific ways. Synapses from the ventral posterior nucleus to central TRN cells transmit rapid excitatory currents that depress deeply during repetitive activity, driving phasic spike output. Synapses from the posterior medial thalamic nucleus to edge TRN cells evoke slower, less depressing excitatory currents that drive more persistent spiking. Differences in the intrinsic physiology of TRN cell types, including state-dependent bursting, contribute to these output dynamics. The processing specializations of these two somatosensory TRN subcircuits therefore appear to be tuned to the signals they carry—a primary central subcircuit tuned to discrete sensory events, and a higher-order edge subcircuit tuned to temporally distributed signals integrated from multiple sources. The structure and function of visual TRN subcircuits closely resemble those of the somatosensory TRN. These results provide insights into how subnetworks of TRN neurons may differentially process distinct classes of thalamic information.

DOI: 10.1038/s41586-020-2512-5

Source: https://www.nature.com/articles/s41586-020-2512-5

Nature:《自然》,创刊于1869年。隶属于施普林格·自然出版集团,最新IF:69.504
官方网址:http://www.nature.com/
投稿链接:http://www.nature.com/authors/submit_manuscript.html


本期文章:《自然》:Online/在线发表

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