June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Amacrine Cell-Ganglion Cell Gap Junctional Coupling, but not Ganglion Cell-Ganglion Cell Coupling, Underlies Long Range Interactions in the Retina
Author Affiliations & Notes
  • Kaushambi Roy
    Biological and Vision Sciences, SUNY, College of Optometry, Clifton, New Jersey, United States
  • Stewart A Bloomfield
    Biological and Vision Sciences, SUNY, College of Optometry, Clifton, New Jersey, United States
  • Footnotes
    Commercial Relationships   Kaushambi Roy, None; Stewart Bloomfield, None
  • Footnotes
    Support  NIH Grants EY007360 and EY026024
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 1609. doi:
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      Kaushambi Roy, Stewart A Bloomfield; Amacrine Cell-Ganglion Cell Gap Junctional Coupling, but not Ganglion Cell-Ganglion Cell Coupling, Underlies Long Range Interactions in the Retina. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1609.

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

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Abstract

Purpose : Widely separated retinal ganglion cells (RGCs) can show coherent light-evoked activity that is thought crucial for global object perception (Neuenschwander and Singer, 1996). Since the wide spatial separation between the RGCs precludes common bipolar cell input, we posit that gap junctional coupling between RGCs and polyaxonal (PAC) or wide field amacrine cells (WFACs) that express Cx36 underlies the coherence. We have reported that indirect coupling between ON α-RGCs via PACs/WFACs underlies coherent responses to global stimuli (ARVO 2016). However, whether direct, serial RGC-RGC coupling can also mediate long range coherent activity is unclear and so we tested this idea on RGCs that show only homologous coupling.

Methods : We targeted YFP-expressing ON and OFF α-RGCs in transgenic Kcng/Thy1(kcng4) mice. Light-evoked spike activity was recorded from pairs of widely separated OFF α-RGCs, which show both homologous and heterologous coupling. The kcng4 mice were crossed with Cx36 knockout (KO) mice to obtain OFF α-RGCs that only showed homologous coupling to OFF α-RGC neighbors. Crosscorrelogram functions (CCFs) were computed from responses to rectangles of light restricted to the separate receptive fields of RGC pairs or to a contiguous rectangle that spanned both receptive fields.

Results : Recordings made from pairs of ON α-RGCs showed significant coherence in response to a global light stimulus, which was lost when coupling to PACs/WFACs was ablated in Cx36 KO mice. Likewise, recordings made from pairs of OFF α-RGCs also showed strong coherent activity when a global stimulus was presented. However, in kcng4/Cx36 KO crossed mice, in which coupling to PACs/WFACs was ablated, but direct OFF α-RGC-to-OFF α-RGC coupling remained, the coherent activity to global stimulation was lost.

Conclusions : Our results indicate that gap junctional coupling via Cx36 between PACs/WFACs and ON and OFF α-RGC is critical to the coherent spike activity seen in response to global object presentation. In contrast, direct serial RGC-RGC coupling is inadequate to produce long-range coherent activity. These results suggest that the functional roles played by homologous coupling between RGCs are limited to local interactions.

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

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