Deng Qiudong, Wang Ling, Dong Wei, He Shigang
Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Republic of China.
J Comp Neurol. 2006 Jun 10;496(5):698-705. doi: 10.1002/cne.20959.
We examined the identities of horizontal cell (HC) lateral components in cone terminals and the expression of glutamate receptors on the tips of HC dendrites. We injected A-type horizontal cells (AHCs) with neurobiotin and demonstrated that neurobiotin labeled completely all AHCs within a patch of retina. We converted neurobiotin by using diaminobenzidine and considered labeled processes to be from AHCs and unlabeled processes to be from B-type horizontal cells (BHCs). Three possible combinations of HC dendrites could exist in cone pedicles: both lateral components originating from AHCs, both from BHCs, or one from an AHC and the other from a BHC. EM observations revealed that a majority of cone terminals contained about equal numbers of lateral components originating from each of the two types of HCs and that each of the three possible combinations was present in equal numbers. Localization of different types of glutamate receptors on HC dendritic tips showed that 55% of AHC dendritic tips expressed AMPA receptors and 30% expressed kainate receptors, whereas, in the case of BHCs, 22% of dendritic tips expressed AMPA receptors and 33% expressed kainate receptors. This study suggests that cone photoreceptors feed the light signal equally into networks of AHCs and BHCs and that differential expression of AMPA/kainate receptors by different HCs could account for different functions.
我们研究了视锥终末中水平细胞（HC）侧向成分的特性以及HC树突末端谷氨酸受体的表达。我们用神经生物素注射A型水平细胞（AHC），并证明神经生物素完全标记了视网膜一片区域内的所有AHC。我们用二氨基联苯胺转化神经生物素，并将标记的突起视为来自AHC，未标记的突起视为来自B型水平细胞（BHC）。视锥小足中可能存在三种HC树突的组合：两个侧向成分均来自AHC，均来自BHC，或者一个来自AHC，另一个来自BHC。电子显微镜观察显示，大多数视锥终末含有数量大致相等的源自两种类型HC的侧向成分，并且三种可能的组合数量相等。不同类型谷氨酸受体在HC树突末端的定位表明，55%的AHC树突末端表达AMPA受体，30%表达海人藻酸受体，而对于BHC，22%的树突末端表达AMPA受体，33%表达海人藻酸受体。这项研究表明，视锥光感受器将光信号同等地输入AHC和BHC网络，并且不同HC对AMPA/海人藻酸受体的差异表达可能解释了不同的功能。
