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Anja-Maria Ladek, Andrea Trost, Christian Runge, Falk Schroedl, Clemens Strohmaier, Herbert A Reitsamer; Immunohistochemical characterization of neurotransmitters in the episcleral circulation in rats. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3034.
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© ARVO (1962-2015); The Authors (2016-present)
Episcleral venous pressure (EVP) is an important parameter of steady-state intraocular pressure and recent evidence suggests neuronal influence on EVP. Yet little is known about the innervation and more specifically, the neurotransmitters involved. The present study aims at identifying possible neurotransmitter candidates for the episcleral circulation in rats.
Four previously untreated, enucleated, immersion fixated rat eyes, taken from three animals were cut into serial sections using a cryostat, followed by standard immunohistochemistry. Additionally to the neurotransmitter under investigation, each slide was stained with antibodies against smooth muscle actin and neurofilament (200kDa).
Throughout the slides neurofilament positive cells could be identified in close proximity to the vascular endothelium. These cells showed synapse like structures and stained positive for synaptophysine. Furthermore, they stained positively for ChAT, Galanin, CGRP, Substance P and PGP 9.5. Staining with antibodies against nNOS, Tyrosine Hydroxylase, Serotonin (5-HT) Transporter and Alarine yielded negative results.
These findings indicate that there is neuronal input to the episcleral circulation. However no assumption can be made whether the positively stained structures are of functional significance for the regulation of the episcleral venous pressure and thereby intraocular pressure.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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