title: Dark/light transition and vigilance states modulate jaw-closing muscle activity level in mice.
abstract: Bruxism is associated with an increase in the activity of the jaw-closing muscles during sleep and wakefulness. However, the changes in jaw-closing muscle activity across states of vigilance over a 24-h period are unclear. In this study, we investigated the effects of dark/light transition and sleep/wake state on EMG activity of the masseter (jaw-closing) muscle in comparison with the activity of the upper trapezius muscle (a neck muscle) over a 24-h period in mice. The activities of the masseter and neck muscles during wakefulness were much greater than during non-REM and REM sleep. In contrast, the activities of both muscles slightly, but significantly, decreased during the transition period from dark to light. Histograms of masseter activity during wakefulness and non-REM sleep showed bimodal distributions, whereas the neck muscle showed unimodal activation in all states. These results suggest that the activities of jaw-closing and neck muscles are modulated by both sleep/wake state and dark/light transition, with the latter being to a lesser degree. Furthermore, even during non-REM sleep, jaw-closing muscles display bimodal activation, which may contribute to the occurrence of exaggerated aberrant muscle activity, such as sleep bruxism.
authors.affiliation: Department of Oral Physiology, Showa University School of Dentistry, 1-5-8, Hatanodai, Shinagawa, Tokyo 142-8555, Japan; Department of Prosthodontics, Showa University School of Dentistry, 2-1-1 Kitasenzoku, Ohta, Tokyo 145-8515, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Katayama
authors.affiliation: Department of Oral Physiology, Showa University School of Dentistry, 1-5-8, Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Mochizuki
authors.affiliation: Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, 1-8, Yamadaoka, Suita 565-0871, Osaka, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kato
authors.affiliation: Department of Prosthodontics, Showa University School of Dentistry, 2-1-1 Kitasenzoku, Ohta, Tokyo 145-8515, Japan.
authors.forename: Minako
authors.initials: M
authors.lastname: Ikeda
authors.affiliation: Removable Partial Prosthodontics, Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo, Tokyo 113-8549, Japan.
authors.forename: Yasuha
authors.initials: Y
authors.lastname: Ikawa
authors.affiliation: Department of Oral Physiology, Showa University School of Dentistry, 1-5-8, Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Department of Oral Physiology, Showa University School of Dentistry, 1-5-8, Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Kiyomi
authors.initials: K
authors.lastname: Nakayama
authors.affiliation: Removable Partial Prosthodontics, Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo, Tokyo 113-8549, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Wakabayashi
authors.affiliation: Department of Prosthodontics, Showa University School of Dentistry, 2-1-1 Kitasenzoku, Ohta, Tokyo 145-8515, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Baba
authors.affiliation: Department of Oral Physiology, Showa University School of Dentistry, 1-5-8, Hatanodai, Shinagawa, Tokyo 142-8555, Japan. Electronic address: inouet@dent.showa-u.ac.jp.
authors.forename: Tomio
authors.initials: T
authors.lastname: Inoue
mesh_terms: D000818:Animals; D002012:Bruxism / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography; D004576:Electromyography; D008406:Masseter Muscle / Q000503:physiopathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D012894:Sleep Stages; D064171:Superficial Back Muscles / Q000503:physiopathology*; D014851:Wakefulness
keywords: Bimodal activation; Bruxism; Electromyogram; Mouse; Non-REM sleep; REM sleep