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RJ Jensen, OR Ziv, JF Rizzo; Effect of Epiretinal Vs Transretinal In Vitro Electrical Stimulation of Rabbit Retinal Ganglion Cells . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4473.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Determine the extent to which activation of retinal ganglion cells in rabbit retina is influenced by the location of the return electrode. Methods:Action potentials of individual ganglion cell axons were recorded extracellularly in superfused adult rabbit retinas in a dimly lit room. Ganglion cells were stimulated electrically by a concentric bipolar electrode with a 125 µm inner wire, positioned on the inner retinal surface over the center of the receptive field of a ganglion cell. The electrical stimulus was a 2 msec duration current pulse. The return electrode was either 1) the 325 µm outer sleeve of the bipolar electrode that was located on the inner retinal surface (epiretinal stimulation), or 2) a Ag/AgCl surface located underneath the sclera (transretinal stimulation). Results:The thresholds for electrical stimulation of ganglion cells depended upon the location of the return electrode. This was true for both direct and indirect activation of ganglion cells. Whether a ganglion cell was directly or indirectly activated was based on several criteria: 1) the latency of the response, 2) the response itself (whether it was a single action potential or a burst of action potentials), and 3) the effect of a synaptic blocker or a glutamate receptor antagonist/agonist. When the outer sleeve of the bipolar electrode served as the return electrode, the thresholds ranged from 6.8 to 1500 µA (mean 490 µA) for direct stimulation and from 11 to 400 µA (mean 260 µA) for indirect stimulation. When the Ag/AgCl surface served as the return electrode, the thresholds ranged from 0.55 to 82 µA (mean 20 µA) for direct stimulation and 3 to 38 µA (mean 16 µA) for indirect stimulation. Conclusion:The results of this study indicate that transretinal current is a more effective stimulus for activating ganglion cells within their receptive fields. This is an important consideration in the final design of an epiretinal prosthesis.
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