Nilvadipine, a Ca2+ antagonist, effectively preserves photoreceptor functions in royal college of surgeons rat

The Royal College of Surgeons (RCS) rat is the most extensively studied animal model for understanding the molecular pathology of inherited retinal degeneration, such as retinitis pigmentosa (RP). We recently found lower levels of rhodopsin kinase expression in RCS rats as compared with control rats, leading us to speculate that misregulation of the phototransduction pathways by the low levels of rhodopsin phosphorylation might be a critical step causing the retinal degeneration. Here, effects of suppression of recoverin-dependent inhibition of rhodopsin phosphorylation on the retinal degeneration in RCS rats by lowering intracellular Ca2+ levels by intraperitoneal administration of nilvadipine, a calcium antagonist, and retinal functions and morphology were analyzed. We found that systemic administration of nilvadipine caused remarkable preservation of photoreceptor functions, electroretinogram responses, and retinal morphology in RCS rats during the initial stage of the retinal degeneration. On the basis of these data, it was strongly suggested that nilvadipine is beneficial for the preservation of photoreceptor cells in RCS rats and can potentially be used to treat some RP patients.