Abstract
Abstract: :
Purpose: Many effects of acetylcholine in the vertebrate retina are mediated by nicotinic acetylcholine receptors (nAChRs), a family of both heteromeric and homomeric ACh-gated cation channels. We studied the expression and localization of a-subunits of nAChRs in normal human retina. Methods: Four post mortem normal human eyes were immersion-fixed in 4% paraformaldehyde and 0.5% glutaraldehyde. Cryosections were cut at 12µm and studied by indirect immunofluorescence. Well-characterized and specific monoclonal antibodies to either the α-4 (mAbs 299 and 369) or α-7 (mAbs 306, 307 and 319) subunits of neural nAChRs were used for immunolabeling. Results: The two α-4 specific antibodies stained neuronal somata in the ganglion cell and inner nuclear layers. Based on cell position, size and shape, these labeled cells were identified as ganglion and amacrine cells. These antibodies labeled only a few processes extending in the scleral direction from cells in the ganglion cell layer. All α-7 specific antibodies labeled neuronal somata in the ganglion cell layer and in the inner part of the inner nuclear layer, as well as a few processes from each cell layer directed toward the inner plexiform layer. The mAbs 306 and 307 less strongly labeled other neuronal somata in the inner nuclear layer; they also stained a relatively sparse subset of cone outer segments. These antibodies stained no laminated fibers in the inner plexiform layer, and no specific immunolabeling was evident in choroid or sclera. Conclusions: nAChRs containing either α-4 or α-7 subunits are expressed in normal human retina, most prominently by ganglion and/or amacrine cells. These localizations indicate potential roles for both heteromeric and homomeric nAChRs in human retina.
Keywords: 305 acetylcholine • 541 receptors: pharmacology/physiology • 490 neurotransmitters/neurotransmitter systems