title: Jaw movement-related primary somatosensory cortical area in the rat.
abstract: It has anatomically been revealed that the rostral part of the rat primary somatosensory cortex (S1) directly projects to the dorsal part of the trigeminal oral subnucleus (dorVo) and the dorsal part of juxtatrigeminal region (dorVjuxt), and that the dorVo and dorVjuxt contain premotoneurons projecting directly to the jaw-opening or jaw-closing motoneurons in the trigeminal motor nucleus (Vmo). However, little is known about how the rostral S1 regulates jaw movements in relation to its corticofugal projections. To address this issue, we performed intracortical microstimulation of the rat rostral S1 by monitoring jaw movements and electromyographic (EMG) activities. We for the first time found that low-frequency long-train stimulation of the rostral S1 induced single sustained opening of the jaw with elevated EMG activities of the anterior digastric muscles (jaw-opener). The effective sites for the low-frequency long-train stimulation overlapped the S1 sites where traditional high-frequency short-train stimulation was effective to induce single twitch-like jaw movement. We also found that the effective sites for the two kinds of train stimuli were included in the rostral S1 area, which has previously been identified to send direct projections to the dorVo or the dorVjuxt. Specifically, the most effective stimulation sites for the two kinds of train stimuli were located in the rostralmost part of S1 which has been reported to emanate strong direct projections to the dorVjuxt but less to the dorVo. Therefore, the present study suggests that the rat rostral S1, especially its rostralmost part, plays an important role in controlling jaw movements by activation of direct descending projections from the rostral S1 to the trigeminal premotoneuron pools, especially to the dorVjuxt.
authors.affiliation: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan; Department of Acupuncture, Takarazuka University of Medical and Health Care, Takarazuka, Hyogo 666-0162, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Uchino
authors.affiliation: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Higashiyama
authors.affiliation: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kato
authors.affiliation: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Haque
authors.affiliation: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors.forename: F
authors.initials: F
authors.lastname: Sato
authors.affiliation: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Tomita
authors.affiliation: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tsutsumi
authors.affiliation: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Moritani
authors.affiliation: Division of Oral Physiology, Niigata University Graduate School of Medical and Dental Sciences, Niigata 951-8514, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yamamura
authors.affiliation: Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan. Electronic address: yoshida@dent.osaka-u.ac.jp.
authors.forename: A
authors.initials: A
authors.lastname: Yoshida
mesh_terms: D000818:Animals; D001931:Brain Mapping; D004558:Electric Stimulation; D004576:Electromyography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D007839:Functional Laterality; D006735:Horseradish Peroxidase / Q000378:metabolism; D007568:Jaw / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013003:Somatosensory Cortex / Q000502:physiology*
chemical_list: D006735:Horseradish Peroxidase
keywords: Corticofugal; Intracortical microstimulation; Primary somatosensory cortex; SI; Trigeminal motoneuron