Abstract
Purpose: :
Previously we demonstrated that transcorneal electrical stimulation (TES) promotes the survival of axotomized retinal ganglion cells (RGCs) in adult rats (Morimoto et al, IOVS 2005). In this sudy we further investigated the optimal parameters of TES for the survival of axotomized RGCs in adult rats.
Methods: :
Adult male Wistar rats were used. Seven days after injection of Fluorogold (FG), a fluorescent tracer for retrograde labeling of RGCs, into the superior colliculi, the left optic nerve (ON) was transected 3 mm from the posterior eye pole. TES was applied immediately after ON transection for 1-hour through concentric bipolar electrodes on a contact lens. Following pulse parameters were changed separately: pulse duration (0.5-5 ms/phase), current intensity (50-300 µA), and frequency of current pulses (0.5-100 Hz). Seven days after ON transection, both the left (transected) and right (intact) eyes were enucleated, then the retinas were flatmounted. The surviving FG-labeled RGCs were counted in 12 areas covering the whole retina under a fluorescent microscope, and the densities of RGCs were determined.
Results: :
Seven days after ON transection with sham stimulation, the mean RGC density (1221±176 cells/mm2 (mean ± SD), n = 8) significantly decreased to 52 % of intact retinas (2357±150 cells/mm2, n = 12). TES exerted the neuroprotective effect on injured RGCs depending on the stimulation parameters. TES at 1-3 ms/phase pulse duration were effective, the mean RGC densities were 82- 85 % of intact value (P < 0.05 vs Sham, n = 6, respectively). TES of 100 and 200 µA were also effective, 80-85 % of intact value (P < 0.05 vs Sham, n = 6, each). TES at 1-20 Hz were also effective, 80- 85% of intact value (P < 0.05 vs Sham,n = 6, respectively).
Conclusions: :
Survival-promoting effects of TES on the axotomized RGCs depend on the stimulation parameters of TES. These results propose the beneficial information for the clinical application of TES for patients with various optic nerve diseases.
Keywords: neuroprotection • ganglion cells • trauma