April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Activity of Corneal Cold Thermoreceptor Nerve Endings Encodes Tear Fluid Hyperosmolality in Mice
Author Affiliations & Notes
  • Carlos Belmonte
    Instituto de Oftalmología Fernández-Vega, Fundacion de Investigación Oftalmológica, Oviedo, Spain
    Instituto de Neurociencias, Univ Miguel Hernandez-CSIC, San Juan de Alicante, Spain
  • Andres Parra
    Instituto de Neurociencias, Univ Miguel Hernandez-CSIC, San Juan de Alicante, Spain
  • Omar Gonzalez
    Instituto de Oftalmología Fernández-Vega, Fundacion de Investigación Oftalmológica, Oviedo, Spain
    Oftalmología, Universidad de Oviedo, Oviedo, Spain
  • Jesus Merayo-Lloves
    Instituto de Oftalmología Fernández-Vega, Fundacion de Investigación Oftalmológica, Oviedo, Spain
    Oftalmología, Universidad de Oviedo, Oviedo, Spain
  • Juana Gallar
    Instituto de Neurociencias, Univ Miguel Hernandez-CSIC, San Juan de Alicante, Spain
  • Footnotes
    Commercial Relationships Carlos Belmonte, None; Andres Parra, None; Omar Gonzalez, None; Jesus Merayo-Lloves, None; Juana Gallar, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 3057. doi:
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      Carlos Belmonte, Andres Parra, Omar Gonzalez, Jesus Merayo-Lloves, Juana Gallar; Activity of Corneal Cold Thermoreceptor Nerve Endings Encodes Tear Fluid Hyperosmolality in Mice. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3057.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: To study the effect of NaCl-induced hyperosmolality (325-1005 mOsm/Kg) on corneal cold thermoreceptor and polymodal nociceptor nerve terminal impulse (NTI) activity in mice.

Methods: Mice eyes were excised and mounted in a recording chamber, superfused with iso-osmolal (309mOsm) physiological saline at basal corneal temperature (34°C). Electrical activity was recorded from individual corneal cold endings using glass pipettes applied onto the corneal surface. Spontaneous activity (SA) at 34°C and firing responses to cooling ramps to 20°C were explored. SA and responses to cooling were also analyzed under controlled high osmolality values (325-1005mOsm/Kg) obtained through increases of NaCl concentration.

Results: Osmolality elevations at basal temperature (34°C) linearly increased the ongoing NTI frequency of cold thermoreceptors (mean rate= 0.34 imp/s per 10 mOsm). NTI frequency increase became significant with osmolality values over 340mOsm. Activation of corneal polymodal nociceptor endings by hyperosmolal solutions started at comparatively higher values (600mOsm and over). Analysis of the combined effect of hyperosmolality and cooling evidenced that about 50% of the increased firing response was attributable to hyperosmolality. High osmolality solutions also altered the firing pattern and shape of cold and polymodal NTIs, which became flattened and slower probably due to a reduction of local membrane currents.

Conclusions: Exposure of the mice eye surface to hyperosmolal solutions obtained by increasing NaCl concentration is an effective stimulus to excite corneal cold thermoreceptors. Combined effects of hyperosmolality and temperature reductions as occurs in dry eye conditions build-up an increased sensory inflow to the brain that may underllie the development of dryness sensations and augmented blinking rate experienced by dry eye disease patients.

Keywords: 486 cornea: tears/tear film/dry eye • 565 innervation: sensation  
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