Select noxious stimuli induce changes on corneal nerve morphology

Deborah M. Hegarty, Sam M. Hermes, Katherine Yang, Sue Aicher

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The surface of the cornea contains the highest density of nociceptive nerves of any tissue in the body. These nerves are responsive to a variety of modalities of noxious stimuli and can signal pain even when activated by low threshold stimulation. Injury of corneal nerves can lead to altered nerve morphology, including neuropathic changes which can be associated with chronic pain. Emerging technologies that allow imaging of corneal nerves in vivo are spawning questions regarding the relationship between corneal nerve density, morphology, and function. We tested whether noxious stimulation of the corneal surface can alter nerve morphology and neurochemistry. We used concentrations of menthol, capsaicin, and hypertonic saline that evoked comparable levels of nocifensive eye wipe behaviors when applied to the ocular surface of an awake rat. Animals were sacrificed and corneal nerves were examined using immunocytochemistry and three-dimensional volumetric analyses. We found that menthol and capsaicin both caused a significant reduction in corneal nerve density as detected with β-tubulin immunoreactivity 2 hr after stimulation. Hypertonic saline did not reduce nerve density, but did cause qualitative changes in nerves including enlarged varicosities that were also seen following capsaicin and menthol stimulation. All three types of noxious stimuli caused a depletion of CGRP from corneal nerves, indicating that all modalities of noxious stimuli evoked peptide release. Our findings suggest that studies aimed at understanding the relationship between corneal nerve morphology and chronic disease may also need to consider the effects of acute stimulation on corneal nerve morphology.

Original languageEnglish (US)
Pages (from-to)2019-2031
Number of pages13
JournalJournal of Comparative Neurology
Volume525
Issue number8
DOIs
StatePublished - Jun 1 2017

Fingerprint

Menthol
Capsaicin
Neurochemistry
Nerve Tissue
Tubulin
Chronic Pain
Cornea
Chronic Disease
Immunohistochemistry
Technology
Pain
Peptides

Keywords

  • CGRP
  • confocal microscopy
  • immunocytochemistry
  • RRID: AB_10063408
  • RRID: AB_2315777
  • RRID: AB_2492288
  • RRID: AB_572217
  • RRID: SCR_007370
  • RRID: SCR_013672
  • RRID: SCR_014199
  • TRP channels
  • β-tubulin

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Select noxious stimuli induce changes on corneal nerve morphology. / Hegarty, Deborah M.; Hermes, Sam M.; Yang, Katherine; Aicher, Sue.

In: Journal of Comparative Neurology, Vol. 525, No. 8, 01.06.2017, p. 2019-2031.

Research output: Contribution to journalArticle

Hegarty, Deborah M. ; Hermes, Sam M. ; Yang, Katherine ; Aicher, Sue. / Select noxious stimuli induce changes on corneal nerve morphology. In: Journal of Comparative Neurology. 2017 ; Vol. 525, No. 8. pp. 2019-2031.
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