期刊
INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
卷 58, 期 1, 页码 404-415出版社
ASSOC RESEARCH VISION OPHTHALMOLOGY INC
DOI: 10.1167/iovs.16-20033
关键词
corneal sensory nerves; thermoreceptors; corneal innervation; polymodal nociceptors; mechanonociceptors
资金
- Consejeria de Economia y Empleo del Gobierno del Principado de Asturias, Spain [FC-15-GRUPIN14-141]
- FEDER funds from the European Union
- Fundacion Ramon Areces
- Caja Rural de Asturias
- Ministerio de Economia y Competitividad of Spain
- FEDER [SAF2014-54518-C3-1-R, SAF2014-54518-C3-2-R]
- Spanish State Research Agency, through the Severo Ochoa'' Programme for Centres of Excellence in RD [SEV-2013-0317]
PURPOSE. To define the firing properties of sensory nerve terminals innervating the adult mouse cornea in response to external stimuli of differing modality. METHODS. Extracellular electrical activity of single corneal sensory nerve terminals was recorded in excised eyes of C57BL/6J mice. Eyes were placed in a recording chamber and were continuously superfused with warm saline solution. Nerve terminal impulse (NTI) activity was recorded by means of a glass pipette (tip similar to 50 lm), applied on the corneal surface. Nerve terminal impulse discharges were stored in a computer for offline analysis. RESULTS. Three functionally distinct populations of nerve terminals were identified in the mouse cornea. Pure mechanonociceptor terminals (9.5%) responded phasically and only to mechanical stimuli. Polymodal nociceptor terminals (41.1%) were tonically activated by heat and hyperosmolal solutions (850 mOs.kg(-1)), mechanical force, and/or TRPV1 and TRPA1 agonists (capsaicin and allyl isothiocyanate [AITC], respectively). Cold-sensitive terminals (49.4%) responded to cooling. Approximately two-thirds of them fired continuously at 34 degrees C and responded vigorously to small temperature reductions, being classified as high-background activity, low-threshold (HB-LT) cold thermoreceptor terminals. The remaining one-third exhibited very low ongoing activity at 34 degrees C and responded weakly to intense cooling, being named low-background activity, high-threshold (LB-HT) cold thermoreceptor terminals. CONCLUSIONS. The mouse cornea is innervated by trigeminal ganglion (TG) neurons that respond to the same stimulus modalities as corneal receptors of other mammalian species. Mechano- and polymodal endings underlie detection of mechanical and chemical noxious stimuli while HB-LT and LB-HT cold thermoreceptors appear to be responsible for basal and irritation-evoked tearing and blinking, respectively.
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