Immunohistochemical studies of cone photoreceptors and cells of the inner retina in feline rod-cone degeneration

Previous studies using electroretinography and immunohistochemistry have sh own normal cone function and structure in early stages of hereditary rod-co ne degeneration of Abyssinian cats. To further investigate the cone photore ceptors and the inner retina of dystrophic cats, antibodies against green- and blue-sensitive cones and specific cell types of inner retina were used in seven cats with the recessively inherited rod-cone degeneration, and thr ee normal European short-haired cats. There was a reduction in number of bo th types of cones early in the disease. Changes at early stages of disease also occurred among horizontal cells in which there was an extension and a thickening of their lateral processes. The regular configuration of bipolar cells was changed in the more advanced stages of disease and their apical dendrites were lost. Abnormalities were not observed in the amacrine cells and in the ganglion cell layer in any of the present cases. This study show s that the cone system is morphologically abnormal in young cats at an earl ier stage of disease than previously shown. The present findings also suppo rt the assumption that the inner retina is largely preserved throughout the disease process.