gms | German Medical Science

Objective: Photoreceptor degeneration in neurodegenerative diseases like retinitis pigmentosa leads to blindness. Animal models with a genetically caused retinal degeneration showed that photoreceptor degeneration induces a remodeling process. Little is known about the impact of this process on the electrophysiological connectivity. In this study we investigated the stimulation properties, after photoreceptor degeneration in the retinal dystrophic Royal College of Surgeons (RCS) rat.

Materials & Methods: Isolated pieces of retina were placed with their GC layer facing down onto multi electrode arrays. The retina was epiretinal stimulated and perfused with Ames medium or for investigations on the stimulation circuitry, with pharmacological blockers. Data acquisition was performed with the Multi Channel Setup software.

Results: Epiretinal stimulation of GC with current pulses evoked different types of response patterns. These patterns could be divided by the response latencies and the number of evoked spikes into bursty and single, delay or no response patterns. Inhibition of the excitatory signal pathways with CNQX and D-AP5 seems to have no impact on the evoked response patterns, whereas the blockage of inhibitory signals leads to a variation.

Discussion: Analysis of electrically evoked responses of GC in blind rats showed several response patterns after current stimuli. We assume, that the epiretinal stimulation could introduce, additionally to the direct stimulation of GCs, stimulation cascades within the inner nuclear layer which in turn leads to indirect stimulation of the GC. This finding will be helpful in developing an effective stimulation paradigm for visual prosthesis.

Acknowledgement: This work was supported by DFG Grant WA 1472/6-1