The ability of hyperoxia to limit the effects of experimental detachment in cone-dominated retina

PURPOSE. To determine the ability of oxygen supplementation to ameliorate t he effects of retinal detachment in a cone-dominated retina. METHODS. Retinal detachments were created in the right eyes of ground squir rels and the animals immediately placed in normoxic (room air) or hyperoxic (70% oxygen) conditions for 3 days. The retinas were sampled from differen t regions and investigated morphologically or immunocytochemically by light or confocal microscopy. Agarose embedded sections were immunostained with antibody probes to cytochrome oxidase. synaptophysin medium-to-long wavelen gth-sensitive (M/L) cone opsin, rod opsin, excitatory amino acid transporte r 1 (EAAT1), glutamate synthetase (GS), cellular retinaldehyde-binding prot ein (CRALBP), and peanut agglutinin (PNA) lectin. Retinal wholemounts were labeled with PNA and antibodies to short (S)-wavelength- sensitive cone ops in and rod opsin. Cell death was examined using a TUNEL assay on agarose se ctions or using toluidine blue staining on semithin sections. RESULTS. The percentage of dying cells relative to the total nuclei in the photoreceptor layer was significantly reduced, and the total number of nucl ei was greater in hyperoxic animals. Triple labeling using TUNEL, anti-M/L cone opsin and anti-rod opsin showed that hyperoxia had a remarkable effect both on the reduction of cone cell death and the maintenance of the overal l structure of cone photoreceptors. Analysis of the retinal wholemounts dem onstrated the preservation of PNA, S-cone, and rod opsin antibody labeling in the detachments maintained in hyperoxic conditions. Although the disrupt ion of cytochrome oxidase and synaptophysin was seen in normoxic animals, t here was minimal disruption in hyperoxic animals. Labeling with anti-EAAT1, anti-GS, and anti-CRALBP was increased in the Muller cells of normoxic ani mals with detachments, but was decreased in the hyperoxic animals. CONCLUSIONS. Hyperoxia prevents the degeneration of both rods and cones in retinas heavily dominated by cones and mitigates the effect of detachment o n Muller cell reactivity. The Current results suggest that the rescue of co nes is not secondary to that of rods.