IJPPP Copyright © 2009-All rights reserved. Published by e-Century Publishing Corporation, Madison, WI 53711
Int J Physiol Pathophysiol Pharmacol 2011;3(4):280-287.

Original Article
Unraveling a masticatory - oculomotor neural pathway in rat: Implications for a
pathophysiological neural circuit in human?

Jingdong Zhang, Houcheng Liang, Pifu Luo, Huangui Xiong

Department of Pharmacology and Experimental Neurosciences, University of Nebraska Medical Center, Omaha, NE 68198, USA;
Shanxi Provincial Eye Research Institute and Eye Hospital, 30 Great Southern Street, Xi’an 710002, China; ACM Medical Laboratory,
Unity Health Care System, Rochester, NY 14626, USA.

Received October 7, 2011; accepted October 24, 2011; Epub November 15, 2011; Published December 15, 2011

Abstract: Anterograde tracers were injected into the mesencephalic trigeminal nucleus (Vme) in pons, labeled axons and terminals
were observed in ipsilateral oculomotor (III) and trochlear (IV) nuclei, as well as in interstitial nucleus of Cajar and Darkschewitsch
nucleus (INC/DN), the well-known premotor nuclei to the III/IV, but not in abducens nucleus and central mesencephalic and
paramedian pontine reticular formation (CMRF/PPRF).  Retrogradely labeled INC/DN neurons do ensue from injection of tracers into
the III. Confocal microscopy revealed labeled Vme axonal terminals contact with labeled pre-oculomotor neurons in the INC/DN. In
response to electrical stimulation of trigeminal nerve root (TR) jaw muscle branches, which contains peripheral processes of the jaw
muscle spindle, extracellular unit discharges were recorded in the ipsilateral III/IV and INC/DN. Electromyography (EMG) was also
recorded from superior rectus (SR) and levator palpebrae (LP) following electrical stimulation of the TR. Moreover, stimulation of the TR
induced Fos expression in the INC/DN pre-oculomotor neurons, but not in CMRF/PPRF that harbors horizontal eye moving premotor
neurons. By injection of retrograde tracers into the III combined with Fos immunostain, double labeled pre-oculomotor neurons were
observed in the INC/DN. About 80% of retrogradely labeled III premotor neurons express Fos. These results suggest a neural pathway
from the masticatory Vme neurons to the oculomotor system that is probably involved exclusively in vertical and torsional eye movement
as well as eyelid retraction. The potential relationship between this pathway and Marcus Gunn Syndrome (MGS), a congenital jaw-
winking syndrome, was discussed.   (IJPPP1110002).

Keywords: Mesencephalic trigeminal nucleus; Trigeminal nerve root jaw muscle branches; Oculomotor nucleus; Trochlear nucleus;
Interstitial nucleus of Cajal; Darkschewitsch nucleus

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Address all correspondence to:
Jingdong Zhang, MD, PhD
Department of Pharmacology and Experimental Neurosciences
University of Nebraska Medical Center
Omaha, NE 68198, USA
Tel: 402-559-2780
E-mail: jingdong.zhang@unmc.edu

Huangui Xiong, MD, PhD
Department of Pharmacology and Experimental Neurosciences,
University of Nebraska Medical Center
Omaha, NE 68198, USA
Tel: 402-559-5140
E-mail: hxiong@unmc.edu