Different types of ganglion cell share a synaptic pattern

Abstract

Retinal ganglion cells comprise about 10 morphological types that also differ functionally. To determine whether functional differences might arise partially from differences in excitatory input, we quantified the distributions of ribbon contacts to four mammalian ganglion cell types [brisk-transient (BT), brisk-sustained (BS), local edge (LE), directionally selective (DS)], comparing small vs. large and "sluggish" vs. "brisk." Cells in guinea pig retina were filled with fluorescent dye, immunostained for synaptic ribbons, and reconstructed with their ribbon contacts by confocal microscopy. False-positive contacts were corrected by performing the same analysis on processes that lack synapses: glial stalks and rod bipolar axons. All types shared a domed distribution of membrane that was well fit by a Gaussian function (R(2) = 0.96 +/- 0.01); they also shared a constant density of contacts on the dendritic membrane, both across each arbor and across cell types (19 +/- 1 contacts/100 microm(2) membrane). However, the distributions of membrane across the retina differed markedly in width (BT > DS approximately BS > LE) and peak density (BS > DS > LE > BT). Correspondingly, types differed in peak density of contacts (BS > DS approximately LE > BT) and total number (BS approximately BT > DS > LE). These differences between cell types in spatial extent and local concentration of membrane and synapses help to explain certain functional differences.

Spatial Relationships between GABAergic and Glutamatergic Synapses on the Dendrites of Distinct Types of Mouse Retinal Ganglion Cells across Development

“…It is possible that the patterns of postsynaptic sites on RGCs similarly show differential distributions across their arbors [26], [48], [49]. We therefore mapped the densities of YFPγ2 and PSD95CFP and their ratios across the dendritic arbors of each of three RGC types (Figure 6).…”

Retina is structured to process an excess of darkness in natural scenes

“…Retinas were harvested from adult guinea pigs and prepared for anatomy in accordance with guidelines of the University of Pennsylvania and National Institutes of Health (13). Ganglion cells were identified by staining with Syto 13, and the larger somas were injected with DiI (1% dissolved in absolute ethanol).…”

“…Differences between OFF and ON cells were known for dendritic-field diameter, cell spacing, and coverage (see Introduction). The difference in dendritic branching had not been quantified but was critical, because in retinal ganglion cells, membrane area sets the number of excitatory synapses received over a given retinal area (12,13). These numbers, which we now report, could then be compared with the distributions of information across images.…”

“…Furthermore, OFF arbors (as we quantify here) branch more densely (5) and provide similar dendritic membrane areas as ON arbors. Because the membrane density of excitatory synapses (synapses/μm 2 ) is constant across an arbor and across cell types (12,13), OFF cells receive similar numbers of synapses as their counterpart ON cells but over a narrower visual angle. Thus, synapses are more densely devoted to the OFF array.…”

Some Principles of Retinal Design: The Proctor Lecture

“…Consider a large ganglion cell, the brisk-transient type, with 5000 contacts from high-rate bipolar cells versus a small ganglion cell, the local-edge type, with 500 contacts from lowrate bipolar cells 32 ( Fig. 8, upper).…”