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S. Rahmani, R.E. Marc, S.A. Shippy, J.R. Hetling, L.B. Bogdanowicz; Effects of Diffuse Electrical Stimulation Therapy (EST) on the Retina Investigated in an Animal Model of adRP, the Pigmented P23H Rat . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1053.
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© ARVO (1962-2015); The Authors (2016-present)
Electrical stimulation therapy (EST) has been associated with increased cell survival in sensory systems (vision, auditory) challenged by injury or toxic drugs. Rahmani et al. [ARVO 2005] reported that EST preserved photoreceptor sensitivity during the course of retinal degeneration. Electrophysiological, histological, and biochemical measurements have been made to further understand the effect of EST on the retina in rat.
Full–field corneal electroretinograms (ERG) measured in dark–adapted WT rats, before and directly after 30 min of EST, were compared to results from animals receiving 30 min of background illumination instead of EST. Glutamate levels at the vitreal surface of the retina were measured in vivo before, during, and after a 30 min EST session using a nano–liter volume push–pull perfusion technique. P23H rats undergoing EST therapy (50 min sessions 3x per week, begun at 4 wks of age), and control animals on the same anesthesia regimen, were sacrificed at 16 wks and processed for histology.
The ERG a– and b– wave amplitudes were reduced immediately following 30 min of EST (48% and 40%, respectively); this reduction was dependent on EST duration, and was similar to the reduction obtained from moderate background illumination. Glutamate levels at the vitreal surface were transiently depressed (∼50%) during EST. Histological analysis after 12 weeks of EST showed a significant reduction in outer segment layer and outer nuclear layer thicknesses compared to control animals.
EST, delivered with the parameters used in this study, elicits both short–term (adaptation, glutamate depression) and long–term (preserved sensitivity, increased cell loss) physiological effects. Histological analysis demonstrating increased photoreceptor cell loss at the central pole associated with EST contradicts previous ERG data demonstrating similar a–wave amplitudes in EST and control animals, but may be biased due to the local area of analysis.
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