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A. Bergua, A. Juenemann, A. De Laet, J.P. Timmermans, A. Brehmer, W.L. Neuhuber, F. Schroedl; Topography of Nitrergic Intrinsic Choroidal Neurons (ICN) in the Human Eye . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2805.
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Purpose: Nitrergic intrinsic choroidal neurons (ICN) are one component of the autonomic innervation of the eye in higher primates and birds with unknown function. Up to know, their topography in the human eye was only described in quadrants, being mainly concentrated in temporo-central parts of the choroid (Flügel et al., 1994). In birds, using a millimeter raster, a topography differing within single quadrants was obvious, indicating possible functional differences (Schrödl et al., 2002). Thus, this technique was applied onto human eyes as a basis for further functional investigations. Methods: Meeting the Declaration of Helsinki, five eyes of five body-/cornea donors (53-75 years of age; 5-10 hrs p.m.) were obtained from the departement of anatomy or the cornea bank of the University of Erlangen. Choroids were removed and prepared for NADPH-diaphorase reaction. Neurons were quantified using a millimeter raster and their distribution was plotted as 3-D diagram with the number of neurons represented in the z-axis. Results: The number of ICN per choroid (908-2081) was in accordance with data from the literature (Bergua et al., 1993; Flügel et al., 1994; Triviño et al., 2002). Accumulation of ICN was also temporal-central, but with crescent shape manner and temporal convexity over both temporal quadrants. An area of 8-10 square millimeter almost lacking ICN and most likely corresponding to the macula region was found within this cranio-caudal belt. In an area approximately 2-4 mm around the papilla no ICN were present. Only in one preparation a higher concentration of ICN was found in the nasal-central parts of the choroid, differing from results with neurofilament staining of ICN (Triviño et al., 2002). Conclusions: Assuming a role of nitrergic ICN in ocular blood flow regulation (Bergua et al., 1993; Schrödl et al., 2000) the crescent-shape of ICN in the temporal half may indicate special unknown requirements of blood flow regulation in this area. Topographical differences in NADPH-diaphorase (this study) versus neurofilament stained ICN (Triviño et al., 2002) might indicate the presence of subpopulations of ICN.
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