Activation of Neuropeptide Y Receptors Modulates Retinal Ganglion Cell Physiology and Exerts Neuroprotective Actions In Vitro.

Neuropeptide Y (NPY) is expressed in mammalian retina but the location and potential modulatory effects of NPY receptor activation remain largely unknown. Retinal ganglion cell (RGC) death is a hallmark of several retinal degenerative diseases, particularly glaucoma. Using purified RGCs and ex vivo rat retinal preparations, we have measured RGC intracellular free calcium concentration ([Ca2+]i) and RGC spiking activity, respectively.

Sildenafil Acutely Decreases Visual Responses in ON and OFF Retinal Ganglion Cells.

Purpose: Sildenafil (Viagra), a cGMP-specific phosphodiesterase type 5 inhibitor, is widely used for the treatment of erectile dysfunction and pulmonary hypertension. Clinical studies have reported transient visual impairments in patients after single-dose sildenafil use, suggesting neural involvement in several retinal layers, and also, possibly, retinal ganglion cells (RGCs), which provide the unique output of visual information to the brain. However, the effect of sildenafil on the RGC light responses is poorly understood.

Simulations to study spatial extent of stimulation and effect of electrode-tissue gap in subretinal implants.

We present a finite element based simulation and analysis method to describe the spatial extent of stimulation and the effects of electrode-tissue interactions in subretinal prostheses. In particular, we estimate the threshold stimulation current needed to depolarise and evoke action potentials in the ganglion cells to be stimulated at a particular distance from the electrode. This is achieved through the application of a threshold electric field to a spherical neuronal soma model of a retinal ganglion cell under consideration.

Late histological and functional changes in the P23H rat retina after photoreceptor loss.

Several strategies have been proposed to restore useful vision following photoreceptor degeneration. However, a very few studies have investigated late anatomical changes and functional state of residual retinal neurons after complete photoreceptor loss. We investigated the progressive degeneration of retinal ganglion cells (RGCs) in P23H rats.

Retinal electrophysiology for toxicology studies: applications and limits of ERG in animals and ex vivo recordings.

Assessing retinal drug toxicity is becoming increasingly important as different molecules are now developed for the treatment of neurodegenerative diseases and vascular disorders. In pharmacology and toxicology, the electroretinogram (ERG) and the multielectrode array (MEA) recording techniques can be used to quantify the possible side effects of retino-active xenobiotics. Toxicity testing requires the use of rodent as well as non-rodent models for extrapolation to the human model when determining risk and safety.

Bioluminescent imaging of Ca2+ activity reveals spatiotemporal dynamics in glial networks of dark-adapted mouse retina.

Glial Ca(2+) excitability plays a key role in reciprocal neuron-glia communication. In the retina, neuron-glia signalling is expected to be maximal in the dark, but the glial Ca(2+) signal characteristics under such conditions have not been evaluated. To address this question, we used bioluminescence imaging to monitor spontaneous Ca(2+) changes under dark conditions selectively in Müller cells, the principal retinal glial cells.