The orderly spacing of retinal neurons is commonly regarded as a characteristic feature of retinal nerve cell populations. Exemplars of this property include the horizontal cells and the cholinergic amacrine cells, where individual cells minimize the proximity to like-type neighbors, yielding regularity in the patterning of their somata. Recently, two types of retinal bipolar cells in the mouse retina were shown to exhibit an order in their somal patterning no different from density-matched simulations constrained by soma size but being otherwise randomly distributed. The present study has now extended this finding to a type of retinal amacrine cell, the AII amacrine cell. Voronoi domain analysis revealed the patterning in the population of AII amacrine somata to be no different from density-matched and soma-size-constrained random simulations, while analysis of the density recovery profile showed AII amacrine cells to exhibit a minimal intercellular spacing identical to that for those random simulations: AII amacrine somata were positioned side-by-side as often as chance would predict. Regularity indexes and packing factors (PF) were far lower than those achieved by either the horizontal cells or cholinergic amacrine cells, with PFs also being comparable to those derived from the constrained random simulations. These results extend recent findings that call into question the widespread assumption that all types of retinal neurons are assembled as regular somal arrays, and have implications for the way in which AII amacrine cells must distribute their processes to ensure a uniform coverage of the retinal surface.

中文翻译：

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小鼠视网膜中 AII 无长突细胞镶嵌的体细胞图案与匹配密度和受体细胞大小限制的随机模拟无法区分

视网膜神经元的有序间距通常被认为是视网膜神经细胞群的特征。这种特性的例子包括水平细胞和胆碱能无长突细胞，其中单个细胞最大限度地减少与同类邻居的接近，从而产生其胞体模式的规律性。最近，小鼠视网膜中的两种类型的视网膜双极细胞显示出其体细胞图案的顺序，这与受体细胞大小限制但随机分布的密度匹配模拟没有什么不同。本研究现已将这一发现扩展到一种视网膜无长突细胞，即 AII 无长突细胞。Voronoi 域分析揭示了 AII 无长突胞体群体中的模式与密度匹配和胞体大小受限的随机模拟没有什么不同，而对密度恢复曲线的分析显示，所有无长突细胞表现出与那些随机模拟相同的最小细胞间距：所有无长突胞体并排放置，就像机会预测的那样频繁。规律性指数和堆积因子 (PF) 远低于水平细胞或胆碱能无长突细胞所达到的值，PFs 也与受约束随机模拟得出的那些相当。这些结果扩展了最近的发现，这些发现对所有类型的视网膜神经元都组装成规则的体细胞阵列这一普遍假设提出了质疑，并对所有无长突细胞必须分布其过程以确保均匀覆盖视网膜表面的方式产生影响。