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A. Stett, T. Herrmann; Electrical Stimulation of Degenerated Retina With a Subretinal Implant Causes Temporary Inhibition of the Radial Retinal Pathway. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3019.
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Repetitive stimulation of the retinal network with electrical pulses causes a frequency dependent depression of ganglion cell response (Jensen, 2007, J. Neural Eng). This affects the temporal resolution obtainable by continuous local stimulation by a subretinal implant. Using paired pulses applied to two spatially separated electrodes at different interpulse intervals we investigated 1) the spatial extension of the retinal patch in which response depression occurs after local stimulation, and 2) whether radial and lateral inhibition of retinal signalling is responsible for response depression.
Retina pieces from blind RCS rats (50 to 177 days old) were placed ganglion cell layer down on microelectrode arrays (MEAs). An 8-channel comb electrode array (pitch 80 µm, Thomas Recordings) was used for electrical stimulation of the distal retina. Paired voltage pulses were delivered through an 8-channel stimulus generator. Ganglion cell activity was recorded with the MEA system (Multi Channel Systems). We varied both the spatial and the temporal distance between paired pulses.
The application of paired pulses to one electrode with an interpulse interval of 250 ms and shorter resulted in local depression of ganglion cell activity to 20% after the second pulse. Almost undisturbed activity after the second impulse, and nearly independent of the interpulse interval, was observed when the first pulse was applied by an electrode with a distance > 80 µm to the recording site. In a second set of experiments, where the second pulse was applied to the distant electrode, ganglion cells were found that responded both to the first and second pulse.
We conclude that local electrical stimulation leads to temporary depression of signal transmission in the radial retinal pathway, presumably at the synapses at the axon terminal of bipolar cells. The lateral pathway including amacrine cells is not inhibited as the activation by distant electrodes was not depressed.
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