Evaluation of Inner Retinal Structure in the Aged RCS Rat

Abstract

Abstract: : Purpose: In retinitis pigmentosa (RP), loss of visual function is predominantly due to the loss of rod photoreceptors. A number of labs are currently evaluating whether RP may be treated by replacing the diseased photoreceptors with either healthy cells or a photosensitive prosthetic device. As these efforts are critically dependent upon the maintenance of an intact inner retinal circuitry, we evaluated inner retinal structure and function in a widely used model of photoreceptor degeneration, the RCS rat. Methods: Eyes were collected from deeply anesthetized pigmented dystrophic RCS rats and controls from 3 weeks to 12 months of age, immersion fixed in 4% paraformaldehyde for 30 min, cryoprotected, embedded and sectioned at 10 µm. Immunohistochemistry was completed using standard protocols with the following antibodies: PKC or recoverin, to label rod and cone bipolar cells, respectively, and calretinin, parvalbumin, choline acetyltransferase, or tyrosine hydroxylase to label subclasses of amacrine cells. Results: In addition to observing a retraction of rod bipolar cell projections similar to that previously described (Hanitzsch et al., 1998), we observed an increase in the intensity of recoverin label in cone bipolar cell somas. We found a normal laminar labeling pattern for all amacrine cell markers in the RCS inner nuclear and plexiform layers. Conclusion: This study identified changes in the cone visual pathway which may be important in considering treatment strategies for RP. In comparison, amacrine cell organization appears to be well maintained in the RCS rat during photoreceptor degeneration.

Keywords: immunohistochemistry • retinal degenerations: hereditary • retina: proximal(bipolar, amacrine, and gangli