Does Background Matter? A Comparative Characterization of Mouse Models of Autosomal Retinitis Pigmentosa rd1 and Pde6b-KO.

Many retinal degenerative diseases result in vision impairment or permanent blindness due to photoreceptor loss or dysfunction. It has been observed that Pde6b mice (rd1), which carry a spontaneous nonsense mutation in the gene, have a strong phenotypic similarity to patients suffering from autosomal recessive retinitis pigmentosa. In this study, we present a novel mouse model of retinitis pigmentosa generated through gene knockout using CRISPR/Cas9 technology.

Magnetoreceptory Function of European Robin Retina: Electrophysiological and Morphological Non-Homogeneity.

The avian magnetic compass allows orientation during migration and is shown to function properly under short-wavelength but not long-wavelength visible light. Therefore, the magnetoreceptive system is assumed to be light- and wavelength-dependent and localized in the retina of the eye. Putative candidates for the role of primary magnetosensory molecules are the cryptochromes that are known to be expressed in the avian retina and must be able to interact with phototransduction proteins.

Phototransduction in Anuran Green Rods: Origins of Extra-Sensitivity.

Green rods (GRs) represent a unique type of photoreceptor to be found in the retinas of anuran amphibians. These cells harbor a cone-specific blue-sensitive visual pigment but exhibit morphology of the outer segment typical for classic red rods (RRs), which makes them a perspective model object for studying cone-rod transmutation. In the present study, we performed detailed electrophysiological examination of the light sensitivity, response kinetics and parameters of discrete and continuous dark noise in GRs of the two anuran species: cane toad and marsh frog.

Electroretinographic study of the magnetic compass in European robins.

Migratory birds are known to be sensitive to external magnetic field (MF). Much indirect evidence suggests that the avian magnetic compass is localized in the retina. Previously, we showed that changes in the MF direction could modulate retinal responses in pigeons.

Searching for magnetic compass mechanism in pigeon retinal photoreceptors.

Migratory birds can detect the direction of the Earth's magnetic field using the magnetic compass sense. However, the sensory basis of the magnetic compass still remains a puzzle. A large body of indirect evidence suggests that magnetic compass in birds is localized in the retina.

The effects of dopamine and dopamine receptor agonists on the phototransduction cascade of frog rods.

Purpose: Accumulating evidence suggests that dopamine, the major catecholamine in the vertebrate retina, may modulate cAMP-mediated signaling in photoreceptors to optimize vision in the light/dark cycle. The main putative mechanism of dopamine-induced adaptation changes in photoreceptors is activation of D-like receptors (DR), which leads to a decrease of the intracellular cAMP level and reduction of protein kinase A (PKA) activity. However, the mechanisms by which dopamine exerts its regulating effect on the phototransduction cascade remain largely unknown.

Rejection of the biophoton hypothesis on the origin of photoreceptor dark noise.

Rod photoreceptors of the vertebrate retina produce, in darkness, spontaneous discrete current waves virtually identical to responses to single photons. The waves comprise an irreducible source of noise (discrete dark noise) that may limit the threshold sensitivity of vision. The waves obviously originate from acts of random activation of single rhodopsin molecules.

Origins of the phototransduction delay as inferred from stochastic and deterministic simulation of the amplification cascade.

Purpose: To identify steps of the phototransduction cascade responsible for the delay of the photoresponse.

Methods: Electrical responses of fish () cones and frog rods and cones were recorded with a suction pipette technique and as an aspartate-isolated mass receptor potential from isolated perfused retinas. Special attention was paid to sufficiently high temporal resolution (1-ms flash, 700 Hz amplification bandpass).

Elevated cAMP improves signal-to-noise ratio in amphibian rod photoreceptors.

The absolute sensitivity of vertebrate retinas is set by a background noise, called dark noise, which originates from several different cell types and is generated by different molecular mechanisms. The major share of dark noise is produced by photoreceptors and consists of two components, discrete and continuous. Discrete noise is generated by spontaneous thermal activations of visual pigment.

cAMP controls rod photoreceptor sensitivity via multiple targets in the phototransduction cascade.

In early studies, both cyclic AMP (cAMP) and cGMP were considered as potential secondary messengers regulating the conductivity of the vertebrate photoreceptor plasma membrane. Later discovery of the cGMP specificity of cyclic nucleotide-gated channels has shifted attention to cGMP as the only secondary messenger in the phototransduction cascade, and cAMP is not considered in modern schemes of phototransduction. Here, we report evidence that cAMP may also be involved in regulation of the phototransduction cascade.

Kinetics of turn-offs of frog rod phototransduction cascade.

The time course of the light-induced activity of phototrandsuction effector enzyme cGMP-phosphodiesterase (PDE) is shaped by kinetics of rhodopsin and transducin shut-offs. The two processes are among the key factors that set the speed and sensitivity of the photoresponse and whose regulation contributes to light adaptation. The aim of this study was to determine time courses of flash-induced PDE activity in frog rods that were dark adapted or subjected to nonsaturating steady background illumination.