title: Trigeminal pathways for hypertonic saline- and light-evoked corneal reflexes.
abstract: Cornea-evoked eyeblinks maintain tear film integrity on the ocular surface in response to dryness and protect the eye from real or potential damage. Eyelid movement following electrical stimulation has been well studied in humans and animals; however, the central neural pathways that mediate protective eyeblinks following natural nociceptive signals are less certain. The aim of this study was to assess the role of the trigeminal subnucleus interpolaris/caudalis (Vi/Vc) transition and subnucleus caudalis/upper cervical cord (Vc/C1) junction regions on orbicularis oculi electromyographic (OOemg) activity evoked by ocular surface application of hypertonic saline or exposure to bright light in urethane anesthetized male rats. The Vi/Vc and Vc/C1 regions are the main sites of termination for trigeminal afferent nerves that supply the ocular surface, while hypertonic saline (saline=0.15-5M) and bright light (light=5k-20klux) selectively activate ocular surface and intraocular trigeminal nerves, respectively, and excite second-order neurons at the Vi/Vc and Vc/C1 regions. Integrated OOemg activity, ipsilateral to the applied stimulus, increased with greater stimulus intensities for both modalities. Lidocaine applied to the ocular surface inhibited OOemg responses to hypertonic saline, but did not alter the response to light. Lidocaine injected into the trigeminal ganglion blocked completely the OOemg responses to hypertonic saline and light indicating a trigeminal afferent origin. Synaptic blockade by cobalt chloride of the Vi/Vc or Vc/C1 region greatly reduced OOemg responses to hypertonic saline and bright light. These data indicate that OOemg activity evoked by natural stimuli known to cause irritation or discomfort in humans depends on a relay in both the Vi/Vc transition and Vc/C1 junction regions.
authors.affiliation: Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Moos Tower 18-186, 515 Delaware Street SE, Minneapolis, MN 55455, USA. Electronic address: mrahman@umn.edu.
authors.forename: M
authors.initials: M
authors.lastname: Rahman
authors.affiliation: Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Moos Tower 18-186, 515 Delaware Street SE, Minneapolis, MN 55455, USA.
authors.forename: K
authors.initials: K
authors.lastname: Okamoto
authors.affiliation: Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Moos Tower 18-186, 515 Delaware Street SE, Minneapolis, MN 55455, USA.
authors.forename: R
authors.initials: R
authors.lastname: Thompson
authors.affiliation: Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Moos Tower 18-186, 515 Delaware Street SE, Minneapolis, MN 55455, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Bereiter
mesh_terms: D018686:Anesthetics, Intravenous / Q000494:pharmacology; D000818:Animals; D001767:Blinking / Q000187:drug effects / Q000502:physiology*; D066193:Cervical Cord / Q000187:drug effects / Q000502:physiology; D003035:Cobalt / Q000494:pharmacology; D003315:Cornea / Q000187:drug effects / Q000502:physiology*; D004576:Electromyography; D008012:Lidocaine / Q000494:pharmacology; D008027:Light; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D018373:Peripheral Nervous System Agents / Q000494:pharmacology; D010775:Photic Stimulation; D051381:Rats; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage; D014276:Trigeminal Nerve / Q000187:drug effects / Q000502:physiology*; D014278:Trigeminal Nuclei / Q000187:drug effects / Q000502:physiology; D014520:Urethane / Q000494:pharmacology; D061567:Voltage-Gated Sodium Channel Blockers / Q000494:pharmacology
chemical_list: D018686:Anesthetics, Intravenous; D018373:Peripheral Nervous System Agents; D012462:Saline Solution, Hypertonic; D061567:Voltage-Gated Sodium Channel Blockers; D003035:Cobalt; D014520:Urethane; D008012:Lidocaine; C018021:cobaltous chloride
keywords: corneal reflex; electromyography; ocular pain; orbicularis oculi; synaptic blocked; trigeminal brainstem
references.citation: Exp Brain Res. 1995;107(2):166-80
references.pmid: 8773237
references.citation: Neurosci Lett. 1997 Jan 24;222(1):33-6
references.pmid: 9121716
references.citation: Am J Ophthalmol. 2006 Jul;142(1):82-87
references.pmid: 16815254
references.citation: Pain. 2010 May;149(2):235-242
references.pmid: 20206444
references.citation: Invest Ophthalmol Vis Sci. 2011 Oct 04;52(11):7852-8
references.pmid: 21896840
references.citation: J Comp Neurol. 1988 Jun 15;272(3):370-82
references.pmid: 2843578
references.citation: J Comp Neurol. 1993 May 22;331(4):495-516
references.pmid: 8509507
references.citation: Adv Neurol. 1983;39:727-38
references.pmid: 6660119
references.citation: J Neurosci. 2007 Sep 26;27(39):10414-22
references.pmid: 17898213
references.citation: Exp Eye Res. 2010 Mar;90(3):388-96
references.pmid: 20004193
references.citation: Brain Res. 1991 Aug 16;556(2):209-17
references.pmid: 1933356
references.citation: J Neurosci. 2011 Aug 3;31(31):11256-67
references.pmid: 21813686
references.citation: Neuroscience. 1996 May;72(1):243-54
references.pmid: 8730721
references.citation: J Comp Neurol. 1981 Dec 20;203(4):785-98
references.pmid: 6173403
references.citation: Invest Ophthalmol Vis Sci. 2010 Dec;51(12):6125-30
references.pmid: 20631232
references.citation: Mov Disord. 1987;2(4):227-35
references.pmid: 3504552
references.citation: J Neurosci. 2002 Oct 15;22(20):8808-18
references.pmid: 12388587
references.citation: Ann N Y Acad Sci. 2003 Oct;1004:1-9
references.pmid: 14662442
references.citation: Exp Brain Res. 2005 Jun;163(4):445-56
references.pmid: 15785953
references.citation: Cephalalgia. 2001 Apr;21(3):184-8
references.pmid: 11442552
references.citation: Invest Ophthalmol Vis Sci. 2013 May 07;54(5):3325-32
references.pmid: 23572103
references.citation: Invest Ophthalmol Vis Sci. 2014 Mar 13;55(3):1555-63
references.pmid: 24557346
references.citation: J Neurophysiol. 2000 Aug;84(2):1050-61
references.pmid: 10938327
references.citation: Neurology. 1980 Jul;30(7 Pt 1):782-5
references.pmid: 7190247
references.citation: J Neurophysiol. 1999 Nov;82(5):2092-107
references.pmid: 10561390
references.citation: Neuroscience. 2009 Jun 2;160(4):858-64
references.pmid: 19285114
references.citation: Invest Ophthalmol Vis Sci. 2009 Aug;50(8):3671-9
references.pmid: 19324847
references.citation: Clin Neurophysiol. 2014 Mar;125(3):593-601
references.pmid: 24064248
references.citation: J Neurophysiol. 1997 Jan;77(1):43-56
references.pmid: 9120584
references.citation: Neurosci Lett. 1986 Jan 30;63(3):320-4
references.pmid: 3951756
references.citation: J Neurosci. 1996 Nov 15;16(22):7318-30
references.pmid: 8929438
references.citation: Invest Ophthalmol Vis Sci. 1991 Feb;32(2):387-400
references.pmid: 1993591
references.citation: Exp Brain Res. 2007 Jun;179(4):691-702
references.pmid: 17216149
references.citation: J Neurophysiol. 1995 Jul;74(1):226-48
references.pmid: 7472326
references.citation: Neuroscience. 2010 Aug 11;169(1):455-62
references.pmid: 20417694
references.citation: J Neurosci. 2004 Apr 28;24(17):4224-32
references.pmid: 15115818
references.citation: Neurology. 2008 Oct 14;71(16):1275-82
references.pmid: 18852443
references.citation: J Neurophysiol. 2003 Nov;90(5):2837-49
references.pmid: 12890797
references.citation: J Comp Neurol. 1987 Jul 15;261(3):450-9
references.pmid: 3112189
references.citation: Jpn J Ophthalmol. 1983;27(1):261-70
references.pmid: 6855018
references.citation: J Neurol. 1997 Jan;244(1):30-4
references.pmid: 9007742
references.citation: Neurology. 1985 Jun;35(6):797-801
references.pmid: 4000481
references.citation: Neuroscience. 2010 Oct 13;170(2):678-85
references.pmid: 20643195
references.citation: Invest Ophthalmol Vis Sci. 2001 Aug;42(9):2063-7
references.pmid: 11481273
references.citation: J Neurophysiol. 1998 May;79(5):2593-602
references.pmid: 9582231
references.citation: Prog Neurobiol. 1980;15(1):71-83
references.pmid: 7422875
references.citation: Am J Ophthalmol. 2011 Dec;152(6):900-909.e1
references.pmid: 22019306
references.citation: Neuroscience. 1993 Jun;54(3):809-18
references.pmid: 8332263
references.citation: Eur J Neurosci. 2012 Dec;36(11):3492-9
references.pmid: 22937868