title: Orofacial proprioceptive thalamus of the rat.
abstract: The ascending pathway mediating proprioception from the orofacial region is still not fully known. The present study elucidated the relay of jaw-closing muscle spindle (JCMS) inputs from brainstem to thalamus in rats. We injected an anterograde tracer into the electrophysiologically identified supratrigeminal nucleus (Su5), known to receive JCMS input. Many thalamic axon terminals were labeled and were found mainly contralaterally in a small, unpredicted area of the caudo-ventromedial edge (VPMcvm) of ventral posteromedial thalamic nucleus (VPM). Electrical stimulation of the masseter nerve and passive jaw movements induced large responses in the VPMcvm. The VPMcvm is far from the rostrodorsal part of ventral posterolateral thalamic nucleus (VPL) where proprioceptive inputs from the body are represented. After injection of a retrograde tracer into the electrophysiologically identified VPMcvm, many neurons were labeled almost exclusively in the contralateral Su5, whereas no labeled neurons were found in the principal sensory trigeminal nucleus (Pr5) and spinal trigeminal nucleus (Sp5). In contrast, after injection of a retrograde tracer into the core of VPM, many neurons were labeled contralaterally in the Pr5 and Sp5, but none in the Su5. We conclude that JCMS input excites trigeminothalamic projection neurons in the Su5 which project primarily to the VPMcvm in marked contrast to other proprioceptors and sensory receptors in the orofacial region which project to the core VPM. These findings suggest that lesions or deep brain stimulation in the human equivalent of VPMcvm may be useful for treatment of movement disorders (e.g., orofacial tremor) without affecting other sensations.
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka, 565-0871, Japan. yoshida@dent.osaka-u.ac.jp.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yoshida
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujio
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Sato
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Md Sams Sazzad
authors.initials: MSS
authors.lastname: Ali
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka, 565-0871, Japan.|Department of Oral Medicine and Diagnostic Sciences, College of Dentistry, King Saud University, Riyadh, 11545, Saudi Arabia.
authors.forename: Tahsinul
authors.initials: T
authors.lastname: Haque
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Haruka
authors.initials: H
authors.lastname: Ohara
authors.affiliation: Department of Physical Therapy, Faculty of Health Science, Morinomiya University of Medical Sciences, Osaka, 559-8611, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Moritani
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kato
authors.affiliation: Department of Physiology and Faculty of Dentistry, University of Toronto, Toronto, ON, M5S 1A8, Canada.
authors.forename: Jonathan O
authors.initials: JO
authors.lastname: Dostrovsky
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Tachibana
mesh_terms: D000818:Animals; D001931:Brain Mapping / Q000379:methods; D001933:Brain Stem / Q000502:physiology*; D004558:Electric Stimulation; D004562:Electrocardiography; D005071:Evoked Potentials; D008297:Male; D008406:Masseter Muscle / Q000294:innervation*; D009470:Muscle Spindles / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D056347:Neuroanatomical Tract-Tracing Techniques; D011434:Proprioception; D017208:Rats, Wistar; D013787:Thalamic Nuclei / Q000502:physiology*; D014276:Trigeminal Nerve / Q000502:physiology*
keywords: DBS; Orofacial deep sensation; Supratrigeminal nucleus; Thalamotomy; Trigeminal; VPM