Retinal Temperature Determination Based on Photopic Porcine Electroretinogram.

Objective: Subthreshold retinal laser therapy (SLT) is a treatment modality where the temperature of the retinal pigment epithelium (RPE) is briefly elevated to trigger the therapeutic benefits of sublethal heat shock. However, the temperature elevation induced by a laser exposure varies between patients due to individual differences in RPE pigmentation and choroidal perfusion. This study describes an electroretinography (ERG)-based method for controlling the temperature elevation during SLT.

Determination of basal phosphodiesterase activity in mouse rod photoreceptors with cGMP clamp.

Light regulates cGMP concentration in the photoreceptor cytoplasm by activating phosphodiesterase (PDE) molecules through a G-protein signalling cascade. Spontaneous PDE activity is present in rod outer segments even in darkness. This basal PDE activity (β) has not been determined in wild type mammalian photoreceptor cells although it plays a key role in setting the sensitivity and recovery kinetics of rod responses.

Electrophysiological determination of phosphodiesterase-6 inhibitor inhibition constants in intact mouse retina.

Cyclic nucleotide phosphodiesterases (PDEs) hydrolyze the second messengers cAMP and cGMP. PDEs control numerous cellular processes making them promising targets for the development of therapeutic agents. Unfortunately, many PDE inhibitor molecules are non-selective among PDE classes and efficient methods for quantitative studies on the isoform-specificity of PDE inhibitors in the natural environments of PDEs are unavailable.

Transretinal ERG in Studying Mouse Rod Phototransduction: Comparison With Local ERG Across the Rod Outer Segments.

Purpose: Electroretinography (ERG) is the gold standard in clinical examinations of retinal function. Corneal ERG is widely used for diagnostics, but ERG components from the inner retina complicate quantitative investigations of the phototransduction cascade. Transretinal ERG (TERG) recorded ex vivo enables pharmacologic isolation of signals generated by photoreceptor cells, establishing an appealing electrophysiologic method for diverse studies of phototransduction.

A novel Ca2+-feedback mechanism extends the operating range of mammalian rods to brighter light.

Sensory cells adjust their sensitivity to incoming signals, such as odor or light, in response to changes in background stimulation, thereby extending the range over which they operate. For instance, rod photoreceptors are extremely sensitive in darkness, so that they are able to detect individual photons, but remain responsive to visual stimuli under conditions of bright ambient light, which would be expected to saturate their response given the high gain of the rod transduction cascade in darkness. These photoreceptors regulate their sensitivity to light rapidly and reversibly in response to changes in ambient illumination, thereby avoiding saturation.