Pan Feng, Massey Stephen C
School of Optometry, The Hong Kong Polytechnic University, Hong Kong, Hong Kong SAR, China.
Centre for Eye and Vision Research (CEVR), Hong Kong, Hong Kong SAR, China.
Front Ophthalmol (Lausanne). 2023 Nov 16;3:1173706. doi: 10.3389/fopht.2023.1173706. eCollection 2023.
In the monkey retina, there are two distinct types of axon-bearing horizontal cells, known as H1 and H2 horizontal cells (HCs). In this study, cell bodies were prelabled using 4',6-diamidino-2-phenylindole (DAPI), and both H1 and H2 horizontal cells were filled with Neurobiotin™ to reveal their coupling, cellular details, and photoreceptor contacts. The confocal analysis of H1 and H2 HCs was used to assess the colocalization of terminal dendrites with glutamate receptors at cone pedicles. After filling H1 somas, a large coupled mosaic of H1 cells was labeled. The dendritic terminals of H1 cells contacted red/green cone pedicles, with the occasional sparse contact with blue cone pedicles observed. The H2 cells were also dye-coupled. They had larger dendritic fields and lower densities. The dendritic terminals of H2 cells preferentially contacted blue cone pedicles, but additional contacts with nearly all cones within the dendritic field were still observed. The red/green cones constitute 99% of the input to H1 HCs, whereas H2 HCs receive a more balanced input, which is composed of 58% red/green cones and 42% blue cones. These observations confirm those made in earlier studies on primate horizontal cells by Dacey and Goodchild in 1996. Both H1 and H2 HCs were axon-bearing. H1 axon terminals (H1 ATs) were independently coupled and contacted rod spherules exclusively. In contrast, the H2 axon terminals contacted cones, with some preference for blue cone pedicles, as reported by Chan and Grünert in 1998. The primate retina contains three independently coupled HC networks in the outer plexiform layer (OPL), identified as H1 and H2 somatic dendrites, and H1 ATs. At each cone pedicle, the colocalization of both H1 and H2 dendritic tips with GluA4 subunits close to the cone synaptic ribbons indicates that glutamate signaling from the cones to H1 and H2 horizontal cells is mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors.
在猴视网膜中，存在两种不同类型的有轴突的水平细胞，即H1和H2水平细胞（HCs）。在本研究中，使用4',6-二脒基-2-苯基吲哚（DAPI）对细胞体进行预标记，并用Neurobiotin™填充H1和H2水平细胞，以揭示它们的耦合、细胞细节和光感受器接触。对H1和H2水平细胞进行共聚焦分析，以评估终末树突与视锥小足上谷氨酸受体的共定位。在填充H1细胞体后，标记出了一个由H1细胞组成的大的耦合镶嵌体。H1细胞的树突终末与红/绿视锥小足接触，偶尔也会观察到与蓝视锥小足的稀疏接触。H2细胞也存在染料耦合。它们具有更大的树突野和更低的密度。H2细胞的树突终末优先与蓝视锥小足接触，但在树突野内几乎与所有视锥细胞仍有额外接触。红/绿视锥细胞构成了H1水平细胞输入的99%，而H2水平细胞接收的输入更为平衡，由58%的红/绿视锥细胞和42%的蓝视锥细胞组成。这些观察结果证实了1996年Dacey和Goodchild对灵长类水平细胞早期研究所得到的结果。H1和H₂水平细胞都有轴突。H1轴突终末（H1 ATs）独立耦合，且仅与视杆小球接触。相比之下，如1998年Chan和Grünert所报道的，H2轴突终末与视锥细胞接触，对蓝视锥小足有一定偏好。灵长类视网膜在外网状层（OPL）中包含三个独立耦合的水平细胞网络，分别为H1和H2体细胞树突，以及H1轴突终末。在每个视锥小足处，H1和H2树突尖端与靠近视锥突触带的GluA4亚基的共定位表明，从视锥细胞到H1和H2水平细胞的谷氨酸信号传导是由α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）受体介导的。
