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F. Schroedl, K. Stuebinger, A. Brehmer, W.L. Neuhuber; Intrinsic choroidal neurons (ICN) in the chicken eye . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4286.
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Purpose: Intrinsic choroidal neurons (ICN) are present in the eye of humans and some bird species. They innervate choroidal blood vessels and stromal smooth muscle cells, thus being relevant for the maintenance of ocular homeostasis. In birds, most data are available from duck up to know. Since data from chicken, an established model in experimental ophthalmology, are lacking, the need for morphological analysis of ICN in this species is apparent. Filling this gap, and to reveal the chemical coding of ICN and sources of extrinsic innervation to the chicken eye was aim of this study. Methods: Chicken choroids were processed for double immunohistochemistry of the following markers: neuronal nitric oxide synthase (nNOS)/Galanin (GAL), vasoactive intestinal polypeptide (VIP)/GAL, nNOS/tyrosine hydroxilase (TH). Histochemistry for NADPH–diaphorase was also performed. Cranial ganglia supplying the eye (i.e. ciliary, trigeminal, pterygopalatine and superior cervical ganglia) were immunohistochemically processed for GAL, Somatostatin (SOM), calcitonin gene–related peptide (CGRP), nNOS, TH. Light–, fluorescence–, and confocal laser scanning microscopy was used for documentation. Results: GAL immunoreactivity was found in varicose nerve fibres in the choroidal stroma and perivascular plexus as well as in perikarya of ICN. Here, it was highly colocalized with nNOS (87.3%). Double staining for VIP/GAL revealed a colocalization rate of 79.1%. In double staining for nNOS/TH or GAL/CGRP, ICN were closely apposed by TH and CGRP immunoreactive nerve fibres. In extrinsic sources, choroid (SOM–positive) neurons of the ciliary ganglion were lacking GAL, as did CGRP–positive neurons of the trigeminal ganglion. In the superior cervical ganglion, a subpopulation of TH–positive neurons were immuno–reactive for GAL, whereas GAL and TH were not colocalized in fibres of the choroidal stroma. In the pterygopalatine ganglion, colocalization rate of nNOS/GAL was about 52%, while colocalization rate for VIP/GAL was about 65%, respectively. Conclusions: Despite species differences, these data indicate close similarities of choroidal innervation between chicken and duck. Therefore, further studies on the functional role of ICN can also be performed in chicken.
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