感光神经节细胞驱动小鼠视网膜中的局部抑制回路。

Photoreceptive Ganglion Cells Drive Circuits for Local Inhibition in the Mouse Retina.

机构信息

Interdepartmental Neuroscience Program.

Department of Ophthalmology and Visual Science.

出版信息

J Neurosci. 2021 Feb 17;41(7):1489-1504. doi: 10.1523/JNEUROSCI.0674-20.2020. Epub 2021 Jan 4.

Abstract

Intrinsically photosensitive retinal ganglion cells (ipRGCs) exhibit melanopsin-dependent light responses that persist in the absence of rod and cone photoreceptor-mediated input. In addition to signaling anterogradely to the brain, ipRGCs signal retrogradely to intraretinal circuitry via gap junction-mediated electrical synapses with amacrine cells (ACs). However, the targets and functions of these intraretinal signals remain largely unknown. Here, in mice of both sexes, we identify circuitry that enables M5 ipRGCs to locally inhibit retinal neurons via electrical synapses with a nonspiking GABAergic AC. During pharmacological blockade of rod- and cone-mediated input, whole-cell recordings of corticotropin-releasing hormone-expressing (CRH) ACs reveal persistent visual responses that require both melanopsin expression and gap junctions. In the developing retina, ipRGC-mediated input to CRH ACs is weak or absent before eye opening, indicating a primary role for this input in the mature retina (i.e., in parallel with rod- and cone-mediated input). Among several ipRGC types, only M5 ipRGCs exhibit consistent anatomical and physiological coupling to CRH ACs. Optogenetic stimulation of local CRH ACs directly drives IPSCs in M4 and M5, but not M1-M3, ipRGCs. CRH ACs also inhibit M2 ipRGC-coupled spiking ACs, demonstrating direct interaction between discrete networks of ipRGC-coupled interneurons. Together, these results demonstrate a functional role for electrical synapses in translating ipRGC activity into feedforward and feedback inhibition of local retinal circuits. Melanopsin directly generates light responses in intrinsically photosensitive retinal ganglion cells (ipRGCs). Through gap junction-mediated electrical synapses with retinal interneurons, these uniquely photoreceptive RGCs may also influence the activity and output of neuronal circuits within the retina. Here, we identified and studied an electrical synaptic circuit that, in principle, could couple ipRGC activity to the chemical output of an identified retinal interneuron. Specifically, we found that M5 ipRGCs form electrical synapses with corticotropin-releasing hormone-expressing amacrine cells, which locally release GABA to inhibit specific RGC types. Thus, ipRGCs are poised to influence the output of diverse retinal circuits via electrical synapses with interneurons.

摘要

内在光敏视网膜神经节细胞 (ipRGC) 表现出依赖于黑视素的光反应,即使在没有视杆和视锥光感受器介导输入的情况下也能持续存在。除了向前向大脑发出信号外,ipRGC 还通过与无棘突 GABA 能无长突细胞 (AC) 的缝隙连接介导的电突触向后向视网膜内回路发出信号。然而,这些内视网膜信号的靶标和功能在很大程度上仍然未知。在这里,我们在雌雄小鼠中鉴定出一种电路,该电路使 M5 ipRGC 通过与非棘突 GABA 能 AC 的电突触局部抑制视网膜神经元。在药理学阻断视杆和视锥介导的输入后,CRH 表达 AC 的全细胞记录显示持续的视觉反应,需要黑视素表达和缝隙连接。在发育中的视网膜中,在睁眼之前,ipRGC 介导的对 CRH AC 的输入较弱或不存在,这表明该输入在成熟视网膜中具有主要作用(即在与视杆和视锥介导的输入并行的情况下)。在几种 ipRGC 类型中,只有 M5 ipRGC 与 CRH AC 表现出一致的解剖和生理耦合。局部 CRH AC 的光遗传学刺激直接驱动 M4 和 M5,但不驱动 M1-M3,ipRGC 的 IPSC。CRH AC 还抑制 M2 ipRGC 偶联的放电 AC,证明离散的 ipRGC 偶联中间神经元网络之间存在直接相互作用。总之,这些结果表明电突触在将 ipRGC 活性转化为局部视网膜回路的前馈和反馈抑制方面具有功能作用。黑视素直接在内在光敏视网膜神经节细胞 (ipRGC) 中产生光反应。通过与视网膜中间神经元的缝隙连接介导的电突触,这些独特的光感受器 RGC 也可能影响视网膜内神经元回路的活动和输出。在这里,我们鉴定并研究了一个电突触回路,该回路原则上可以将 ipRGC 活性与已鉴定的视网膜中间神经元的化学输出耦合。具体来说,我们发现 M5 ipRGC 与表达促肾上腺皮质释放激素的无长突细胞形成电突触,后者局部释放 GABA 抑制特定的 RGC 类型。因此,ipRGC 能够通过与中间神经元的电突触影响各种视网膜回路的输出。

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