June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
Characterizing the rod pathway in cone-dominated thirteen-lined ground squirrels
Author Affiliations & Notes
  • Riley Ferguson
    Retinal Neurophysiology, National Eye Institute, Bethesda, Maryland, United States
    University of Cincinnati, Cincinnati, Ohio, United States
  • Francisco Nadal-Nicolás
    Retinal Neurophysiology, National Eye Institute, Bethesda, Maryland, United States
  • Wei Li
    Retinal Neurophysiology, National Eye Institute, Bethesda, Maryland, United States
  • Footnotes
    Commercial Relationships   Riley Ferguson None; Francisco Nadal-Nicolás None; Wei Li None
  • Footnotes
    Support  National Eye Institute Intramural Research Program
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 1649. doi:
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      Riley Ferguson, Francisco Nadal-Nicolás, Wei Li; Characterizing the rod pathway in cone-dominated thirteen-lined ground squirrels. Invest. Ophthalmol. Vis. Sci. 2023;64(8):1649.

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

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Purpose : AII-amacrine bipolar cells are widely accepted as a critical element of scotopic visual pathways in the mammalian retina, and have been well-characterized in mice, rabbit, and non-human primates, all of which are rod-dominant in general. The rod pathway is largely maintained across mammalian eyes, however, the anatomic and physiologic understanding of this pathway in thirteen-lined ground squirrels (TLGS), a cone-dominant species, has been limited and uncertain. We endeavored to characterize the morphologic and functional qualities of the rod pathway in the TLGS.

Methods : Scotopic electroretinograms (ERG) were recorded from the TLGS cohort. We collected and stained TLGS retinas with calretinin antibody which selectively labelled AII-amacrine cells. The same tissue was then stained with PKC-α antibody as described by Mills and Massey (1999). A confocal microscope was used to image the retinal samples and the images were analyzed using Image J and photoshop.

Results : In all TLGS retinas examined, AII-Amacrine cells exhibited connections to the rod bipolar cell pathway, largely conserved as compared to other mammalian eyes, with decreased AII cell density and expanded arborization. AII-amacrine cell retained connections with each other via the gap junctions as demonstrated by Connexin36 labelling. All TLGS tested by ERG demonstrated functional scotopic vision.

Conclusions : The main components of the rod pathway are conserved in the cone-dominated TLGS retina. AII amacrine cells in the TLGS are sparsely populated, matching the diminished rod and rod bipolar cell populations compared to rod-dominant species. AII amacrine cells in the TLGS may be more specialized in the rod pathway than has been demonstrated in the mouse retina, in which AII amacrine cells are also significantly involved in cone pathways. This decrease in spatial density may point to an evolutionary adaptation of the rod pathway in cone-dominated mammalian species. Through full elucidation of the role in AII-amacrine cells, we can better understand their evolutionary function across both rod and cone dominated species.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.


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