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Exp Neurobiol 2018; 27(1): 16-27
Published online February 28, 2018
https://doi.org/10.5607/en.2018.27.1.16
© The Korean Society for Brain and Neural Sciences
Ji-Yeon Lee and Su-Ja Oh*
Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
Correspondence to: *To whom correspondence should be addressed.
TEL: 82-2-2258-7259, FAX: 82-2-536-3110
e-mail: sujaoh@catholic.ac.kr
The retinal degeneration resulting from elevated intraocular pressure was evaluated through functional and morphological analyses, for better understanding of the pathophysiology of glaucoma. Ocular hypertension was induced via unilateral episcleral venous cauterization in rats. Experimental time was set at 1 and 3 days, and 1, 2, 4, and 8 weeks post-operation. Retinal function was analyzed using electroretinography. For morphological analysis, retinal tissues were processed for immunochemistry by using antibodies against the calcium-sensing receptor and calcium-binding proteins. Apoptosis was analyzed using the TUNEL method and electron microscopy. Amplitudes of a- and b-wave in scotopic and photopic responses were found to be reduced in all glaucomatous retinas. Photopic negative response for ganglion cell function significantly reduced from 1-day and more significantly reduced in 2-week glaucoma. Calcium-sensing receptor immunoreactivity in ganglion cells remarkably reduced at 8 weeks; conversely, protein amounts increased significantly. Calcium-binding proteins immunoreactivity in amacrine cells clearly reduced at 8 weeks, despite of uneven changes in protein amounts. Apoptosis appeared in both photoreceptors and ganglion cells in 8-week glaucomatous retina. Apoptotic feature of photoreceptors was typical, whereas that of ganglion cells was necrotic in nature. These findings suggest that elevated intraocular pressure affects the sensitivity of photoreceptors and retinal ganglion cells, and leads to apoptotic death. The calcium-sensing receptor may be a useful detector for alteration of extracellular calcium levels surrounding the ganglion cells.
Keywords: electroretinography, Ca2+-sensing receptor, retinal ganglion cell, apoptosis, glaucoma, rats