Bright flash response recovery of mammalian rods in vivo is rate limited by RGS9.

J Gen Physiol 2017 Apr 16;149(4):443-454. Epub 2017 Mar 16.

Center for Neuroscience, University of California, Davis, Davis, CA 95618

The temporal resolution of scotopic vision is thought to be constrained by the signaling kinetics of retinal rods, which use a highly amplified G-protein cascade to transduce absorbed photons into changes in membrane potential. Much is known about the biochemical mechanisms that determine the kinetics of rod responses ex vivo, but the rate-limiting mechanisms in vivo are unknown. Using paired flash electroretinograms with improved signal-to-noise, we have recorded the amplitude and kinetics of rod responses to a wide range of flash strengths from living mice. Bright rod responses in vivo recovered nearly twice as fast as all previous recordings, although the kinetic consequences of genetic perturbations previously studied ex vivo were qualitatively similar. In vivo, the dominant time constant of recovery from bright flashes was dramatically reduced by overexpression of the RGS9 complex, revealing G-protein deactivation to be rate limiting for recovery. However, unlike previous ex vivo recordings, dim flash responses in vivo were relatively unaffected by RGS9 overexpression, suggesting that other mechanisms, such as calcium feedback dynamics that are strongly regulated by the restricted subretinal microenvironment, act to determine rod dim flash kinetics. To assess the consequences for scotopic vision, we used a nocturnal wheel-running assay to measure the ability of wild-type and RGS9-overexpressing mice to detect dim flickering stimuli and found no improvement when rod recovery was speeded by RGS9 overexpression. These results are important for understanding retinal circuitry, in particular as modeled in the large literature that addresses the relationship between the kinetics and sensitivity of retinal responses and visual perception.

Download full-text PDF

Source
http://dx.doi.org/10.1085/jgp.201611692DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5379920PMC
April 2017
Get 20% Off Journals at LWW.com

Similar Publications

A new PDE6A missense variant p.Arg544Gln in rod-cone dystrophy.

Doc Ophthalmol 2021 Feb 21. Epub 2021 Feb 21.

Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, 105-8461, Japan.

Purpose: Thus far, only one Japanese patient with autosomal recessive rod-cone dystrophy (AR-RCD) associated with the phosphodiesterase 6A gene (PDE6A) has been reported. The purpose of this study was to analyze the clinical features of a Japanese female patient with AR-RCD with a novel missense variant in PDE6A.

Methods: We performed whole-exome sequencing (WES) to identify the disease-causing variant and a comprehensive ophthalmic examination including full-field electroretinography (ERG). Read More

View Article and Full-Text PDF
February 2021

Rod photoreceptors avoid saturation in bright light by the movement of the G protein transducin.

J Neurosci 2021 Feb 15. Epub 2021 Feb 15.

Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, CA 90095-7000, USA

Rod photoreceptors can be saturated by exposure to bright background light, so that no flash superimposed upon the background can elicit a detectable response. This phenomenon, called increment saturation, was first demonstrated psychophysically by Aguilar and Stiles and has since been shown in many studies to occur in single rods. Recent experiments indicate, however, that rods may be able to avoid saturation under some conditions of illumination. Read More

View Article and Full-Text PDF
February 2021

Equilibrium phase diagram and thermal responses of charged DNA-virus rod-suspensions at low ionic strengths.

Authors:
Kyongok Kang

Sci Rep 2021 Feb 10;11(1):3472. Epub 2021 Feb 10.

Institute of Biological Information Processing, IBI-4, Biomacromolecular Systems and Processes, Forschungszentrum Jülich, Jülich, Germany.

The collective behavior of DNA is important for exploring new types of bacteria in the means of detection, which is greatly interested in the understanding of interactions between DNAs in living systems. How they self-organize themselves is a physical common phenomenon for broad ranges of thermodynamic systems. In this work, the equilibrium phase diagrams of charged chiral rods (fd viruses) at low ionic strengths (below a few mM) are provided to demonstrate both replicas of (or self-organized) twist orders and replica symmetry breaking near high concentration glass-states. Read More

View Article and Full-Text PDF
February 2021

Big trees drive forest structure patterns across a lowland Amazon regrowth gradient.

Sci Rep 2021 Feb 9;11(1):3380. Epub 2021 Feb 9.

Programa de Pós-Graduação Em Biodiversidade Tropical, Universidade Federal Do Amapá (UNIFAP), Rod. Juscelino Kubitscheck, Km 02, Macapá, AP, 68902-280, Brazil.

Degraded Amazonian forests can take decades to recover and the ecological results of natural regeneration are still uncertain. Here we use field data collected across 15 lowland Amazon smallholder properties to examine the relationships between forest structure, mammal diversity, regrowth type, regrowth age, topography and hydrology. Forest structure was quantified together with mammal diversity in 30 paired regrowth-control plots. Read More

View Article and Full-Text PDF
February 2021

A patient diagnosed with Galloway-Mowat syndrome presenting with a rod-cone functional anomaly with electronegative dark-adapted ERGs.

Doc Ophthalmol 2021 Feb 6. Epub 2021 Feb 6.

Department of Ophthalmology, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH, 43205, USA.

Purpose: Galloway-Mowat syndrome (GAMOS) is a clinically heterogenous and rare condition classically described as the combination of nephrotic syndrome associated with brain anomaly and delays in development. It was first reported in the literature in 1968 by Galloway W.H and Mowat A. Read More

View Article and Full-Text PDF
February 2021