Efferent and afferent innervation of primate trabecular meshwork and scleral spur
J. M. Selbach1,2, J. Gottanka2, M. Wittmann2, K.-P. Steuhl1, E. Lütjen-Drecoll2
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 immuno-histochemically 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), galanin (GAL) and with the NADPH-diaphorase reaction. The distribution of the terminals was compared with that of a -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-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 being in contact with the cribriform elastic network. In the posterior SS of monkey eyes there were large terminals similar to those previously described in human eyes.
Conclusions: We show for the first time that in the primate TM and SS there are cholinergic and nitrergic nerve terminals which 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.
1 Universitäts-Augenklinik Essen, Hufelandstr. 55, 45122 Essen
2 Anatomisches Institut II, Universität Erlangen, 91054 Erlangen