Abstract
AII amacrine cells have been found in all mammalian retinas examined and play an important role for visual processing under both scotopic and photopic conditions. Whereas ultrastructural investigations have provided a detailed understanding of synaptic connectivity, there is little information available with respect to quantitative properties and variation of cellular morphology. Here, we performed whole-cell recordings from AII amacrine cells in rat retinal slices and filled the cells with fluorescent dyes. Multi-photon excitation microscopy was used to acquire image stacks and after deconvolution, we performed quantitative morphological reconstruction by computer-aided manual tracing. We reconstructed and performed morphometric analysis on 43 AII amacrine cells, with a focus on branching pattern, dendritic lengths and diameters, surface area, and number and distribution of dendritic varicosities. Compared to previous descriptions, the most surprising result was the considerable extent of branching, with the maximum branch order ranging from approximately 10–40. We found that AII amacrine cells conform to a recently described general structural design principle for neural arbors, where arbor density decreases proportionally to increasing territory size. We confirmed and quantified the bi-stratified morphology of AII amacrine cells by analyzing the arborizations as a function of retinal localization or with Sholl spheres. Principal component and cluster analysis revealed no evidence for morphological subtypes of AII amacrines. These results establish a database of morphometric properties important for studies of development, regeneration, degeneration, and disease processes, as well as a workflow compatible with compartmental modeling.
Highlights
AII amacrine cells have been found in all mammalian retinas examined and play an important role for visual processing under both scotopic and photopic conditions
Visual targeting and identification of AII amacrine cells in retinal slices To ensure that only AII amacrine cells were included among the cells to be imaged and reconstructed, two main criteria had to be met during targeting in retinal slices
We took considerable care to only record and fill cells that displayed the morphological characteristics of AII amacrines, as judged by their appearance in retinal slices imaged with infrared Dodt gradient contrast (IR-DGC) videomicroscopy (Fig. 1a)
Summary
AII amacrine cells have been found in all mammalian retinas examined and play an important role for visual processing under both scotopic and photopic conditions. The focus in the present study is on the AII amacrine cell, traditionally considered an axon-less interneuron, which is found in all mammalian retinas investigated and plays an important role in both scotopic and photopic processing of visual signals There is a surprising lack of information, with respect to the quantitative aspects of AII amacrine cell morphology, including information about the variability of morphological properties. Cells can be filled in live tissue (in vitro or in vivo) with tracers such as biocytin (Horikawa and Armstrong 1988) and Neurobiotin (Kita and Armstrong 1991) or with fluorescent dyes, using either sharp microelectrodes or patch pipettes These techniques offer the opportunity of correlated morphological and physiological investigations (Jaeger 2001; Blackman et al 2014). Confocal microscopy is well-suited for imaging dye-filled neurons after tissue fixation, but that again introduces potential problems with tissue shrinkage and distortion
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call