Cervical sympathectomy causes photoreceptor-specific cell death in the rat retina

Changes in the regulation of the vasculature of the eye may be related to some age-related ocular diseases. We have previously shown that loss of sympathetic innervation, as can normally occur with age, resulted in substantial vascular growth of the choroid. The current study was designed to determine whether changes induced by sympathetic denervation causes significant loss of photoreceptors and increased glial cell reactivity in the retina. Sympathetic denervation was performed followed by immunohistochemistry, TUNEL staining, and protein expression analysis to investigate photoreceptor loss. There was a significant reduction (30%) in photoreceptor numbers in the sympathectomized eye. This loss was due to apoptosis, as there was over a doubling in apoptotic cell numbers after sympathectomy. This loss of photoreceptors in the sympathectomized eye resulted in a significantly reduced width of the outer nuclear layer of the retina when compared to the contralateral eye. Increased glial fibrillary acidic protein (GFAP) staining was also noted after sympathectomy in the ganglion cell layer with streaking toward the bipolar cell layer. These results suggest that loss of sympathetic innervation may cause significant changes to the physiology of the choroid.