Nitric oxide modulates the temporal properties of the glutamate response in type 4 OFF bipolar cells

PLoS One. 2014 Dec 2;9(12):e114330. doi: 10.1371/journal.pone.0114330. eCollection 2014.

Abstract

Nitric oxide (NO) is involved in retinal signal processing, but its cellular actions are only partly understood. An established source of retinal NO are NOACs, a group of nNOS-expressing amacrine cells which signal onto bipolar, other amacrine and ganglion cells in the inner plexiform layer. Here, we report that NO regulates glutamate responses in morphologically and electrophysiologically identified type 4 OFF cone bipolar cells through activation of the soluble guanylyl cyclase-cGMP-PKG pathway. The glutamate response of these cells consists of two components, a fast phasic current sensitive to kainate receptor agonists, and a secondary component with slow kinetics, inhibited by AMPA receptor antagonists. NO shortened the duration of the AMPA receptor-dependent component of the glutamate response, while the kainate receptor-dependent component remained unchanged. Application of 8-Br-cGMP mimicked this effect, while inhibition of soluble guanylate cyclase or protein kinase G prevented it, supporting a mechanism involving a cGMP signaling pathway. Notably, perfusion with a NOS-inhibitor prolonged the duration of the glutamate response, while the NO precursor L-arginine shortened it, in agreement with a modulation by endogenous NO. Furthermore, NO accelerated the response recovery during repeated stimulation of type 4 cone bipolar cells, suggesting that the temporal response properties of this OFF bipolar cell type are regulated by NO. These results reveal a novel cellular mechanism of NO signaling in the retina, and represent the first functional evidence of NO modulating OFF cone bipolar cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Glutamic Acid / metabolism*
  • Nitric Oxide / physiology*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, AMPA / metabolism
  • Retinal Cone Photoreceptor Cells / cytology
  • Retinal Cone Photoreceptor Cells / metabolism*

Substances

  • Receptors, AMPA
  • Nitric Oxide
  • Glutamic Acid

Grants and funding

Regular FONDECYT grant 1120513 from CONICYT, Chile (to OS), Postdoctoral FONDECYT grant 3140599 from CONICYT, Chile (to AHV) and Millennium Institute Centro Interdisciplinario de Neurociencia de Valparaíso P09-022-F from ICM-1114 ECONOMIA, Chile. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.