Omar González-González1, Federico Bech1, Juana Gallar2, Jesús Merayo-Lloves1, Carlos Belmonte3. 1. Instituto Universitario Fernández-Vega, Universidad de Oviedo & Fundación de Investigación Oftalmológica, Oviedo, Spain. 2. Instituto de Neurociencias, Universidad Miguel Hernández-Consejo Superior de Investigaciones Cientificas, San Juan de Alicante, Spain. 3. Instituto Universitario Fernández-Vega, Universidad de Oviedo & Fundación de Investigación Oftalmológica, Oviedo, Spain 2Instituto de Neurociencias, Universidad Miguel Hernández-Consejo Superior de Investigaciones Cientificas, San Juan de Alicante, Spain.
Abstract
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 ∼ 50 μm), 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 mOsm·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°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°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.
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 ∼ 50 μm), 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 mOsm·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°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°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.
Authors: Carlos Belmonte; Jason J Nichols; Stephanie M Cox; James A Brock; Carolyn G Begley; David A Bereiter; Darlene A Dartt; Anat Galor; Pedram Hamrah; Jason J Ivanusic; Deborah S Jacobs; Nancy A McNamara; Mark I Rosenblatt; Fiona Stapleton; James S Wolffsohn Journal: Ocul Surf Date: 2017-07-20 Impact factor: 5.033
Authors: Anton Delwig; Shawnta Y Chaney; Andrea S Bertke; Jan Verweij; Susana Quirce; Delaine D Larsen; Cindy Yang; Ethan Buhr; Russell VAN Gelder; Juana Gallar; Todd Margolis; David R Copenhagen Journal: Vis Neurosci Date: 2018-01 Impact factor: 3.241
Authors: Tina B McKay; Yashar Seyed-Razavi; Chiara E Ghezzi; Gabriela Dieckmann; Thomas J F Nieland; Dana M Cairns; Rachel E Pollard; Pedram Hamrah; David L Kaplan Journal: Prog Retin Eye Res Date: 2018-11-16 Impact factor: 21.198