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S. Rahmani, J.R. Hetling, L.B. Bogdanowicz; Electrical Stimulation Therapy for Retina Investigated in a Rat Model of adRP . Invest. Ophthalmol. Vis. Sci. 2005;46(13):509.
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Purpose: Electrical stimulation has been implicated in increased cell survival in sensory systems (vision, auditory) challenged by injury or toxic drugs. These findings motivate the present pilot study, in which electrical stimulation therapy (EST) is investigated for potential benefit in retinal degenerative disease, using an animal model of autosomal dominant retinitis pigmentosa, the pigmented P23H rat. Methods: Animals received one hour of EST 3x a week beginning at 25 days of age (n = 2). EST consisted of repeated trains of biphasic current pulses delivered via a Ag/AgCl electrode in contact with the OS cornea through a layer of artificial tears, referenced to a second Ag/AgCl electrode placed in the mouth. A single littermate control underwent the same anesthetic procedure and corneal electrode placement; DS eyes in stimulated animals also served as controls. Retinal health was evaluated by analyzing the amplitude and sensitivity of the electroretinogram (ERG) a–wave recorded at 5 and 8 weeks. Amplitude–intensity data were fit with the function A/Am = 1 – exp(–k I), where Am is the maximum a–wave amplitude, I is the flash strength, and k reflects response sensitivity (for all fits, 0.85 < R2 < 1.00, mean = 0.95). Results: The maximum ERG a–wave peak amplitudes showed no consistent trend between 5 and 8 week measurements in all 3 animals. Between 5 and 8 weeks, the parameter k changed by –64% (control) and +13%, –7% (stimulated animals). In stimulated animals, maximum a–wave amplitudes and k values in OS (stimulated) and DS (control) responses were similar at 8 weeks. Conclusions: These preliminary data suggest that EST may delay a progressive decrease in photoreceptor sensitivity, however the small sample size prevents conclusive statistical measures. Similarity between OS and DS eyes in EST animals suggests that any benefit of EST may not be restricted to the eye in contact with the stimulating electrode. These animals will be followed for 24 weeks (the period of rapid degeneration in this animal model), and sample size will be increased as animals become available.
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