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J. Michael Selbach, Johannes Gottanka, Markus Wittmann, Elke Lütjen–Drecoll; Efferent and Afferent Innervation of Primate Trabecular Meshwork and Scleral Spur. Invest. Ophthalmol. Vis. Sci. 2000;41(8):2184-2191.
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purpose. To determine the correlation between nerve terminals and cells or
extracellular matrix (ECM) components in different portions of the
primate trabecular meshwork (TM) and scleral spur (SS).
methods. Serial sagittal and tangential sections through the anterior segments
of 10 cynomolgus monkey eyes and 12 human eyes were investigated
immunohistochemically with antibodies against the vesicular
acetylcholine transporter (VACHT), vasoactive intestinal polypeptide
(VIP), tyrosine-hydroxylase (TH), neuropeptide Y (NPY), substance P
(SP), calcitonin gene-related peptide (CGRP), and galanin (GAL) and
with a reduced nicotinamide adenine dinucleotide phosphate–diaphorase
(NADPHd) reaction. The distribution of the terminals was compared with
that of α-smooth-muscle actin (SMA) staining in TM and SS. The
relationship between terminals and adjacent cells or ECM components was
also studied in ultrathin sections through the TM and SS of 11 monkey
eyes cut in sagittal, tangential, and frontal planes.
results. NADPHd-positive nerve terminals were present, especially in the outer
portion of both human and monkey TM and in the SS. VACHT-immunoreactive
(IR) fibers were found in human but not in monkey SS and TM. The fibers
were most numerous in the elongated SS and posterior TM where most
cells also stained for SMA. SP- and CGRP-IR nerve endings were also
more numerous in the outer TM and SS than in the inner TM.
Ultrastructurally, staining for SP was seen in nerve endings containing
mitochondria and dense core vesicles and was in contact with the
cribriform elastic network. In the posterior SS of monkey eyes were
large terminals similar to those previously described in human eyes.
conclusions. The results show for the first time that in the primate TM and SS,
there are cholinergic and nitrergic nerve terminals that could induce
contraction and relaxation of TM and SS cells. Terminals in contact
with the elastic-like network of the TM and containing SP-IR resemble
afferent mechanoreceptor-like terminals in other parts of the body.
These findings raise the possibility that the TM may have some ability
to self-regulate aqueous humor outflow.
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