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Ultrastructural Reconstruction of ON Cone Bipolar Cell Projective Fields In The Inner Plexiform Layer of The Rabbit Retina

retina reconstruction

This abstract was presented at the 2014 FASEB Summer Research Conference in Saxtons River, Vermont by J. Scott Lauritzen, Crystal L. Sigulinsky, Noah T. Nelson, Nathan R. Sherbotie, Danny P. Emrich, Rebecca L. Pfeiffer, Jefferson R. Brown, John V. Hoang, Joshua M. Dudleston, Carl B. Watt, Kevin Rapp, Marguerite V. Shaw, Jia-Hui Yang, James R. Anderson, myself and Robert E. Marc.

Purpose: Functional mapping in tiger salamander shows that bipolar cell (BC) projective fields far exceed their axonal fields, and directly implicates wide-field GABAergic amacrine cells (wf γACs) and gap junctions (Asari & Meister, 2014). Strikingly, single BCs exert differential effects on functionally distinct ganglion cells (GCs), likely achieved by privatized amacrine cell (AC) presynaptic inhibition to specific BC-GC synaptic pairs (Asari & Meister, 2012). To address whether BC projective fields in the mammal are equally broad, wf γAC- and gap junction-dependent, and GC type unselective, we reconstructed all electrical and chemical synaptic partners of a single ON cone BC in the inner plexiform layer of the rabbit retina, and searched BC-GC synaptic pairs for differential synaptic inhibition.

Methods: Cells in retinal connectome 1 (RC1) were annotated with Viking viewer, and explored via connectivity visualizations and 3D rendering (Anderson et al., 2011). Small molecule signals embedded in RC1, e.g. GABA, glycine, and L-glutamate, combined with morphological reconstruction and connectivity analysis allow robust cell classification. We used the MacNeil et al. (2004) rabbit BC classification scheme.

Results: CBb5w 593 is one of 20 ON cone BCs of this class in RC1. This CBb5w is presynaptic to 17 distinct GCs and 262 AC processes, and postsynaptic to 228 AC processes. The majority of these ACs are wf γACs. We estimate this BC forms synapses with 50 unique ACs. Asari & Meister (2014) found that single bipolar cell projective fields range up to 1 mm, far beyond a BC axonal field, and differentially drive multiple classes of GC. We discovered BC-BC within- and cross-class coupling and lateral inhibition that construct sign-conserving and sign-inverting projective fields to many distinct ganglion cell classes across the entire 0.25 mm diameter of RC1, much greater than a 60 µm BC axonal field. Cross-class projections access a broader set of GCs than expected from in-class projections alone. The BC-BC coupling is independent of BC-AII AC coupling. 94% of the CBb5w 593 BC-GC synaptic pairs receive feedback inhibition within the varicosity of the ribbon, but the number of feedback synapses is highly variable (coefficient of variation = 0.81). 35% of the BC-GC pairs receive feedforward inhibition within 2 microns of the postsynaptic density.

Conclusions: Mammalian BCs use novel cross-class topologies to distribute signals to a wide range of GCs and establish projective fields similar to those discovered in non-mammalian species. BC-BC within- and cross-class coupling and lateral inhibition via wf γACs establish sign-conserving and sign-inverting projective fields, respectively, up to 1 mm diameters. BC-GC synaptic pairs overwhelmingly employ feedback vs. feedforward inhibition to modulate signaling, and the numbers of feedback synapses are highly variable across these pairs, accounting for privatized and differential GC responses to the same BC drive.

Categories: Literature-Publications, Science, Ultrastructure.

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4 Responses

  1. Just ran onto your blog this morning – vectored from the supermoon reference on scoop.it. Just wondering if you think adaptive optics images of living retinas is useful? I spent my career developing the technology for the Air Force and introduced it to David Williams at the University of Rochester for use in imaging human living retinas.

    I am also an X-T1 fan and do astrophotography. I’ll look around your flickr site and blog (when I figure out how to run it).

    Cheers
    Bob Fugate

    • Hey Bob,

      Thanks for the note. Wow, what a crazy small world. Yes, I absolutely believe that AO imaging is useful for ophthalmology and retinal research. In fact, it is going to be critical to determine how far along people are in retinal degenerative diseases so we can learn what the best intervention points are going to be for rescues or cures for blinding diseases that are currently in development. I talked a little bit about AO in the retina here on the blog after visiting some colleagues in Wisconsin a couple months ago. http://prometheus.med.utah.edu/~bwjones/2014/01/visit-to-medical-college-of-wisconsin/

      The AO approaches you have helped develop are truly impressive. Years ago, I sat in on a brief where some folks were using ground based AO to visualize structures in orbit which was pretty fascinating. The Soviets had some efforts as well that were somewhat out in the open, but the application of these technologies to so many areas of science, engineering and intelligence has been and will continue to be an amazing feat.

  2. Bryan,

    Wow, it IS a small world. Glad to see you believe AO is useful for your research field. Looked at your previous blog reference and you have done a good job reporting on it. It is quite satisfying for me to see it growing, especially in astronomy but also in retinal research. I am mostly retired except for occasional consulting and now enjoying photography as a passion. I live in Albuquerque, and New Mexico is a target rich environment. I also venture into Utah but now that I have the time need to do it on a more extended basis.

    Bob



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