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Sensory and sympathetic innervation of the mouse and guinea pig corneal epithelium
Author(s) -
Ivanusic Jason J.,
Wood Rhian J.,
Brock James A.
Publication year - 2013
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.23207
Subject(s) - biology , anatomy , free nerve ending , epithelium , nerve plexus , corneal epithelium , ganglion , guinea pig , trigeminal nerve , trigeminal ganglion , sensory system , neuroscience , cornea , endocrinology , genetics
This study used immunohistochemistry, retrograde tracing, and high‐resolution confocal microscopy to explore the structure and neurochemistry of nerve terminals in the corneal epithelium of mice and guinea pigs. In both species, sub‐basal nerves formed a plexus in the basal epithelium. Some axons had bulbar endings within the basal epithelium, but most projected perpendicularly from sub‐basal nerves to within a few micrometers of the epithelial surface. Three morphologies for these nerve terminals were identified. Simple terminals did not branch after leaving the sub‐basal nerves and ended with a single, bulbar swelling. Ramifying terminals branched in the squamous cell layer, forming horizontal fibers that ran parallel to the surface and terminated with single bulbar swellings. Complex terminals branched as they approached the epithelial surface, forming a cluster of highly branched fibers with multiple bulbar endings. Calcitonin gene‐related peptide immunolabeled (peptidergic) axons ended mostly in simple terminals, whereas transient receptor potential cation channel subfamily M member 8 immunolabeled (cold receptor) axons ended almost exclusively in complex terminals. Retrograde labeling identified discrete subpopulations of corneal afferent neurons in the trigeminal ganglion. Tyrosine hydroxylase‐immunolabeled (sympathetic) nerve terminals originating from the superior cervical ganglion occurred throughout the corneal epithelium of mice, but only in the basal epithelium of guinea pigs. These findings demonstrate that nerve terminals in the corneal epithelium of mice and guinea pigs can be distinguished on the basis of their morphology and neurochemistry, and suggest that nerve terminals with different sensory modalities can be defined on the basis of their morphology. J. Comp. Neurol. 521:877–893, 2013. © 2012 Wiley Periodicals, Inc.