Spatiotemporal properties of glutamate input support direction selectivity in the dendrites of retinal starburst amacrine cells
- University of Victoria, Canada
- Aarhus University, Denmark
Abstract
The asymmetric summation of kinetically distinct glutamate inputs across the dendrites of retinal 'starburst' amacrine cells is one of the several mechanisms that have been proposed to underlie their direction-selective properties, but experimentally verifying input kinetics has been a challenge. Here, we used two-photon glutamate sensor (iGluSnFR) imaging to directly measure the input kinetics across individual starburst dendrites. We found that signals measured from proximal dendrites were relatively sustained compared to those measured from distal dendrites. These differences were observed across a range of stimulus sizes and appeared to be shaped mainly by excitatory rather than inhibitory network interactions. Temporal deconvolution analysis suggests that the steady-state vesicle release rate was ~ 3 times larger at proximal sites compared to distal sites. Using a connectomics-inspired computational model, we demonstrate that input kinetics play an important role in shaping direction selectivity at low stimulus velocities. Together, these results provide direct support for the 'space-time wiring' model for direction selectivity.
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Author details
Benjamin L Murphy-Baum
Gautam Bhagwan Awatramani
Funding
Canadian Institutes of Health Research (159444)
- Gautam Bhagwan Awatramani
European Research Council (638730)
- Keisuke Yonehara
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All procedures were performed in accordance with the Canadian Council on Animal Care and approved by the University of Victoria's Animal Care Committee, or in accordance with Danish standard ethical guidelines and were approved by the Danish National Animal Experiment Committee (Permission No. 2015-15-0201-00541; 2020-15-0201-00452).
Copyright
© 2022, Srivastava et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Spatiotemporal properties of glutamate input support direction selectivity in the dendrites of retinal starburst amacrine cells
eLife 11:e81533.
https://doi.org/10.7554/eLife.81533
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