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Chuan-Chin Chiao, Yin-Peng Chen; Spatial Distribution of Excitatory Synapses in Mouse Retinal Ganglion Cells. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3403. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Excitatory glutamatergic inputs from bipolar cells in part define the physiological properties of retinal ganglion cells (RGCs). There are around 17-22 types of RGCs in the mouse retina. Although their distinct dendritic morphologies have been characterized systematically, the spatial patterns of excitatory synaptic inputs on different types of RGCs are less known. In this study, we investigate the distribution of excitatory synapses on various types of mouse RGCs.
The particle-mediated gene transfer technique was used to transfect mouse RGCs with PSD95-GFP plasmids. The dendritic morphologies as well as the spatial distribution patterns of excitatory synaptic inputs on the targeted RGCs were visualized and analyzed.
Despite wide variation in the size and morphology of RGCs, the expression of PSD95 puncta follows two general rules: (1) The PSD95 puncta are regularly spaced, in 1-2 μm interval, on local dendritic segments. Thus, the presence of an excitatory synapse creates an exclusion zone that rules out the presence of other synaptic inputs. (2) The spatial distribution of PSD95 puncta in a two-dimensional space is similar for most cell types. The excitatory synapses on primary dendrites are much less, and the density of excitatory inputs peaks at the edge of cell’s dendritic field.
Mapping the spatial pattern of excitatory synapses on RGCs provides explicit structure information that facilitates the understanding of how distribution and localization of excitatory synaptic inputs shape neuron’s responses.
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