Neuroprotective dose response in RCS rats implanted with microphotodiode arrays

Abstract

Neuropreservation of retinal function and structure in RCS rats following implantation of a microphotodiode array (MPA) has been shown in previous studies (Pardue et al. J Neural Eng 2005;2:S39-47; Pardue et al. Invest Ophthalmol Vis Sci 2005;46:674-682). Since microphotodiodes produce electrical currents in proportion to the intensity of incident light, increased light exposure may result in greater neuroprotective effects. Our previous studies suggested that the frequency of light exposure to electroretinogram (ERG) flash stimuli might provide increased neuroprotection. Thus, in this study, we examined the dose response of subretinal electrical stimulation by exposing RCS rats implanted with MPAs to variable durations and combinations of two different lighting regimens: pulsing incandescent bulbs and xenon stimuli from an ERG Ganzfeld. While incandescent light regimens did not produce any significant differences in ERG function, we found significantly greater dark-adapted ERG b-wave amplitudes in RCS rats that received weekly vs. biweekly ERGs over the course of 8 weeks of follow-up. These results suggest that subretinal electrical stimulation may be optimized to produce greater neuroprotective effects by dosing with periodic higher current. © 2012 Springer Science+Business Media, LLC.