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T Morimoto, T Miyoshi, H Sawai, T Inoue, T Fujikado, Y Tano, Y Fukuda; Neuroprotective Effects of Electrical Stimulation on the Axotomized Retinal Ganglion Cells in Vivo . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2184.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the effects of electrical stimulation on the survival of axtomized retinal ganglion cells (RGCs) in vivo. Methods: Adult male Wistar rats were used. Five days after injection of Fluorogold, a fluorescent tracer for retrograde labeling into the superior colliculi, the left optic nerve (ON) was transected ∼3 mm from the posterior eye pole. Electrical stimulation was commenced within ten minutes after ON cut and lasted for 2 hours. The electrical stimuli were monophasic current pulses (50µs), delivered at 20Hz, from an isolated constant-current stimulator. Animals were devided into 5 subgroups according to the intensity of electric current; 0(sham), 20, 30, 50, 70µA (n=4, each). In sham stimulation group, the bipolar electrode was attached to ON stump without electrical stimulation. Seven days after ON transection, the animals were perfused with 4% paraformaldehyde. Both eyes were enucleated, then the retinas were dissected and flatmounted to count the surviving RGCs under a fluorescent microscope. Densities of RGCs were calculated by counting the number of Fluorogold-labeled neurons in 12 areas covering the whole retina. Results: In normal retinas, the mean density of RGCs was 2401 ± 150 cells/mm2 (mean ± SD) (n=8). In ON cut and sham stimulation groups, the mean densities of RGCs significantly decreased to 53% and 54% of the density of normal retina, respectively (n=4, each, p<0.05). On the other hand, electrical stimulation increased the densities of surviving RGCs, depending on the intensity of electric current. While the mean density of RGCs in the retina with electrical stimulation of 20µA was 64% of the normal RGC density, the density at 30µA significantly increased to 76% and electrical stimulation of 50µA showed the greatest neuroprotective effect, 83% of normal value (p<0.05 compared with ON cut, respectively). At the intensity of 70µA, the surviving RGC density was 75% (p<0.05), less than the density at 50µA. Conclusion: Electrical stimulation of the ON stump immediately after transection enhanced the survival of RGCs in vivo. Further experiments are required to elucidate the mechanism underlying the neuroprotective effects.
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