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Steven Walston, Andrew Weitz, Mark S Humayun, Robert Chow, James D Weiland; Comparison of the Electrical Stimulation Response Thresholds and Spatial Activation of Mouse and Rat Retinal Ganglion Cells using Calcium Imaging. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1837.
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© ARVO (1962-2015); The Authors (2016-present)
To validate the mouse as a model for experiments combining calcium imaging and electrical stimulation of the retina.
Calcium imaging was used to determine retinal ganglion cell (RGC) activation profiles in C57BL/6 mice. Mice of 6-12 weeks age were given an intravitreal injection of AAV2-CAG-GCaMP5G to transduce retinal cells with the calcium indicator GCaMP5G. Two weeks post injection the retina was extracted and mounted RGC side down on a microelectrode array and incubated in heated and oxygenated Ames' sodium bicarbonate solution. The retina was stimulated through a 75-μm electrode. Stimuli included trains of 0.06-ms, 1-ms and 25-ms cathodic-first, controlled current pulses with monotonically increasing amplitudes. RGC calcium fluorescence was recorded and response thresholds were determined with custom software. RGC thresholds and spatial activation in mouse retina were compared to those in Long-Evans rat retina.
RGC thresholds in mouse retina (n = 5) were lowest near the stimulating electrode. 0.06-ms and 1-ms stimuli activated RGCs close to the electrode at low stimulation amplitudes and activated passing axons at slightly higher amplitudes. Axonal stimulation resulted in antidromic activation of peripheral RGCs. 25-ms stimuli did not activate axons. These spatial activation results are in agreement with data found in the Long-Evans rat retina. However, the RGC thresholds recorded in mouse retina are approximately 2-3 times greater than those found in rat retina for each of the stimulus durations tested.
The spatial activation profiles of RGCs in response to epiretinal electrical stimulation are in agreement with those found in rat retina. These results validate the mouse as a suitable model for experiments combining calcium imaging and electrical stimulation.
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