The spatio-temporal pattern of photoreceptor degeneration in the aged rd/rd mouse retina.

Photoreceptor degeneration in the retina of the rd/rd (retinal degeneration) mice has been studied using immunocytochemistry with antisera against cone- and rod-opsin. The rd/rd mice exhibited different regional specific rates of degeneration for rods and cones. As early as postnatal day 25, cells labelled with the rod-opsin and cone-opsin antisera disappeared preferently from the central retina. Whereas in the inferior half of the retina, degeneration subsequently proceeded towards the periphery, this did not occur in the dorsal hemisphere. By the age of 100 days, many cells immunoreactive for the cone-opsin antiserum and a few cells immunoreactive for the rod-opsin antiserum were located in an area of the dorsal retina. The ventral retina lacked labelled elements at this age. Finally, rd/rd mice at one year or 600 days of age contained a similar number of cone-opsin immunopositive cells (approximately 2000-2800 cells), occupying almost the same area in the retina as that found at 100 days of age. A photoreceptor candidate for the entrainment of non-visual photoreception probably remains in the cone population in aged rd/rd mice.