Morphology and neurochemistry of canine corneal innervation.
OBJECTIVE
To determine the architectural pattern and neuropeptide content of canine corneal innervation.


METHODS
Corneal nerve fibers in normal dog eyes were labeled immunohistochemically with antibodies against protein gene product (PGP)-9.5, calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP), and tyrosine hydroxylase (TH). Relative innervation densities and distribution patterns for each fiber population were assessed qualitatively by serial line-drawing reconstructions and quantitatively by computer-assisted analyses.


RESULTS
More than 99% of all corneal PGP-9.5-immunoreactive (IR) nerves contained both CGRP and SP, approximately 30% contained TH, and none contained VIP. Distribution patterns of corneal PGP-9.5-, CGRP-, SP-, and TH-IR nerves were indistinguishable, except that TH-IR fibers were absent from the corneal epithelium. Morphologically, canine corneal innervation consisted of a rich anterior stromal plexus, divided on the basis of morphologic criteria into anterior and posterior levels, and a rich epithelial innervation, characterized by large numbers of horizontally oriented, basal epithelial "leash" formations. Leash axons in all quadrants of the corneal epithelium oriented preferentially toward a common locus in the perilimbal cornea.


CONCLUSIONS
The results of this study demonstrate for the first time the detailed architectural features, distinctive basal epithelial leash orientations, and peptidergic content of canine corneal innervation. The normal innervation pattern described in this study will provide other investigators with essential baseline data for assessing corneal nerve alterations in canine patients with spontaneous chronic corneal epithelial defects (SCCED) and other ocular diseases or injuries.
Marfurt
C F
CF
Department of Anatomy and Cell Biology, Northwest Center for Medical Education, Indiana University School of Medicine, Gary, 46408, USA. cmarfurt@meded.iun.indiana.edu
Murphy
C J
CJ
Florczak
J L
JL
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis; D003315:Cornea / Q000294:innervation*; D004285:Dogs / Q000033:anatomy & histology*; D007124:Immunoenzyme Techniques; D009412:Nerve Fibers / Q000737:chemistry; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009448:Neurochemistry; D013373:Substance P / Q000032:analysis; D013564:Sympathetic Nervous System / Q000033:anatomy & histology* / Q000737:chemistry*; D013869:Thiolester Hydrolases / Q000032:analysis; D014276:Trigeminal Nerve / Q000033:anatomy & histology* / Q000737:chemistry*; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis; D043222:Ubiquitin Thiolesterase; D014660:Vasoactive Intestinal Peptide / Q000032:analysis
D009419:Nerve Tissue Proteins; D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D014446:Tyrosine 3-Monooxygenase; D013869:Thiolester Hydrolases; D043222:Ubiquitin Thiolesterase; D015740:Calcitonin Gene-Related Peptide