Pannexin 1 Is Critically Involved in Feedback from Horizontal Cells to Cones.

Mitali Poovayya,Wim De Graaff,Valentina Cenedese,Georg Zoidl,Maarten Kamermans,Tamás Csikós

doi:10.3389/fnmol.2017.00403

Abstract

Retinal horizontal cells (HCs) feed back negatively to cone photoreceptors and in that way generate the center/surround organization of bipolar cell receptive fields. The mechanism by which HCs inhibit photoreceptors is a matter of debate. General consensus exists that horizontal cell activity leads to the modulation of the cone Ca-current. This modulation has two components, one fast and the other slow. Several mechanisms for this modulation have been proposed: a fast ephaptic mechanism, and a slow pH mediated mechanism. Here we test the hypothesis that the slow negative feedback signal from HCs to cones is mediated by Panx1 channels expressed at the tips of the dendrites of horizontal cell. We generated zebrafish lacking Panx1 and found that the slow component of the feedback signal was strongly reduced in the mutants showing that Panx1 channels are a fundamental part of the negative feedback pathway from HCs to cones.

Highlights

A fundamental feature of the vertebrate visual system is that many of its neurons have receptive fields with a center/surround organization
We determined whether the overall organization of the outer retina was intact in the various mutant zebrafish
In the present article we show that Panx1 channels are critically involved in negative feedback from horizontal cells (HCs) to cones

Summary

Introduction

A fundamental feature of the vertebrate visual system is that many of its neurons have receptive fields with a center/surround organization. Each HC receives input from multiple cones and neighboring HCs are strongly coupled electrically HCs feed back negatively to cones and in that way generate the surround responses of the BCs via a process called lateral inhibition (see for instance: Chalupa and Werner, 2003). In addition to this there is some evidence that HCs might feed back positively to cones (Jackman et al, 2011)

Methods

Results

Conclusion