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J Feher, A Papale, L Gualdi, C Balacco GabrieliOphthalmic Neuroscience Program; INTRINSIC NERVOUS PLEXUS OF THE HUMAN CHORIOCAPILLARY:An ultrastructural study . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2622.
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Purpose: An intrinsic nervous plexus of the human choroid, composed of ganglion cells and their dendrites, was described first in details by Amilcare Bietti in 1897. Several further studies confirmed these observations and suggested its role in the regulation of choroidal blood flow. The aim of our study was to describe the ultrastructure of these nerves and their relation to the choriocapillaries. Methods: Twelve autopsy human eyes were studies by transmission electron microscopy using standard techniques. Results: Neuronal cell bodies of round and slightly oval shape were found in the choriocapillary layer at the posterior pole of the eye: mostly in the intercapillary connective tissue, but also external or even internal to the choriocapillaries. They have poorly electrodens cytoplasm which contains a few small mitochondria and several dilated smooth surface endoplasmic reticulum, some of them continuous with the nuclear membrane. Most dendrites formed close contact with the capillary wall, separated from the endothelial cells by a thin basement membrane. Although, some dendrites were extended to the elastic layer of the Bruch's membrane, none of them contact retinal pigment epithelium. The cytoplasm of dendrites showed similar features to that of the cell body. Thin basement membrane surrounds both cell bodies and dendrites. Almost the whole circumference of choriocapillaries were free of pericytes. Conclusion: Our study represents the first ultrastructural description of a nervous plexus in the human choriocapillary layer. The close topographic correlation to endothelial cells suggest an intrinsic nervous control of endothelial functions in both normal conditions and chorioretinal diseases. As very few and poorly developed processes of pericytes were observed, these cells play a minor role in the regulation of choriocapillary blood flow.
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