June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Synaptic inputs to a gamma ganglion cell in rabbit retina
Author Affiliations & Notes
  • David W Marshak
    Neurobiology & Anatomy, McGovern Medical School, Houston, Texas, United States
  • Andrea S Bordt
    Neurobiology & Anatomy, McGovern Medical School, Houston, Texas, United States
  • Diego Perez
    Neurobiology & Anatomy, McGovern Medical School, Houston, Texas, United States
  • Luke Tseng
    Neurobiology & Anatomy, McGovern Medical School, Houston, Texas, United States
  • Weiley S Liu
    Neurobiology & Anatomy, McGovern Medical School, Houston, Texas, United States
  • Crystal Sigulinsky
    John A. Moran Eye Center, Salt Lake City, Utah, United States
  • Daniel Emrich
    John A. Moran Eye Center, Salt Lake City, Utah, United States
  • James S Lauritzen
    John A. Moran Eye Center, Salt Lake City, Utah, United States
  • Carl B Watt
    John A. Moran Eye Center, Salt Lake City, Utah, United States
  • Bryan W Jones
    John A. Moran Eye Center, Salt Lake City, Utah, United States
  • Robert E Marc
    John A. Moran Eye Center, Salt Lake City, Utah, United States
  • Footnotes
    Commercial Relationships   David Marshak, None; Andrea Bordt, None; Diego Perez, None; Luke Tseng, None; Weiley Liu, None; Crystal Sigulinsky, None; Daniel Emrich, None; James Lauritzen, None; Carl Watt, None; Bryan Jones, None; Robert Marc, Signature Immunologics (E)
  • Footnotes
    Support  University of Texas BRAIN seed grant program 363303 (DWM PI), National Eye Institute Research Grant EY02576 (REM PI).
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 2580. doi:
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    • Get Citation

      David W Marshak, Andrea S Bordt, Diego Perez, Luke Tseng, Weiley S Liu, Crystal Sigulinsky, Daniel Emrich, James S Lauritzen, Carl B Watt, Bryan W Jones, Robert E Marc; Synaptic inputs to a gamma ganglion cell in rabbit retina. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2580.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : There are at least 30 distinct types of mammalian retinal ganglion cells, each sensitive to different features of the visual environment, and these can be grouped according to their morphology. One such group, the gamma cells, was identified more than 40 years ago, but their synaptic inputs have never been described. That was the goal of this study.

Methods : The synaptic inputs to a subtype of gamma cell with dendrites ramifying in the outer sublamina of the inner plexiform layer (IPL) of the rabbit retina were identified in a retinal connectome developed using automated transmission electron microscopy.

Results : The gamma cell was always postsynaptic in the IPL, confirming its identity as a ganglion cell. The local synaptic input should produce relatively weak OFF reposnses to stimuli confined to the center of the gamma cell's receptive field. It typically received only one synapse per bipolar cell from at least 4 types of OFF bipolar cells. Because bipolar cells vary in their response kinetics and contrast sensitivity. each type would provide a small, asynchronous excitatory input. The amacrine cells at the dyad synapses provided only a small amount presynaptic inhibition; reciprocal synapses were observed in only 3 of the 18 ribbon synapses. There was no glycinergic crossover inhibition, another local interaction that would enhance light responses. Local postsynaptic inhibition was somewhat more common; in 6 instances, the bipolar cells presynaptic to the gamma cell or their electrically coupled neighbors also provided input to an amacrine cell that inhibited the gamma cell. The other amacrine cell inputs to the gamma cell should have a much greater impact on the light responses because they are far more numerous. These are from axons and long dendrites of GABAergic amacrine cells, and they provide 60% of all the input. This finding suggests that many types of stimuli in the receptive field surround or outside of the classical receptive field would provide potent inhibition to the gamma cell.

Conclusions : The synaptic inputs rsuggest that gamma cells in rabbit retina would have light responses like their homologs in mouse retina, OFF responses to small stimuli in the receptive field center that are suppressed by a variety of larger stimuli. Thus, they would signal object motion selectively.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Synaptic inputs from bipolar cells (green) and amacrine cells (orange) to the gamma cell (purple).

Synaptic inputs from bipolar cells (green) and amacrine cells (orange) to the gamma cell (purple).

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