Systemic Administration of Phenyl-N-tert-Butylnitrone Protects the Retina from Light Damage

This study was conducted to test the hypothesis that phenyl-N-tert-butylnitrone (PBN), a spin-trapping agent known to cross the blood-brain barrier and protect the brain from ischemia-reperfusion injury, is incorporated into the retina after intraperitoneal injection and protects photoreceptor cells from the damaging effects of constant visible light. Albino rats were injected intraperitoneally with PBN (aqueous solution) or water, or were not injected, and then were placed in constant light (2700 lux) for 24 hours. The incorporation of PBN into the retina was determined by high-performance liquid chromatography. Electroretinograms (ERGs) were recorded before light treatment and 1 and 15 days after the cessation of exposure to constant light. Eyes were taken for histology at each time point and outer nuclear layer (ONL) thickness determined. PBN was incorporated into the retina after intraperitoneal injection. Both control (water-injected and uninjected) groups exposed to constant light maintained only 28% of ONL thickness and 20% of retinal function, compared with the unexposed control group. In contrast, the PBN-treated animals maintained 80% of ONL thickness and exhibited 87% of retinal function. PBN protects the albino rat retina from the damaging effects of constant light stress. That light-induced and hereditary retinal degenerations share certain morphologic hallmarks and follow a similar apoptotic mechanism of degeneration raises the possibility of pharmacologic therapy for hereditary and environmentally induced neurodegenerative disorders.