Heterogeneous activity level of jaw-closing and -opening muscles and its association with arousal levels during sleep in the guinea pig.

Osaka Univ. Graduate School of Dentistry, Dept. of Oral Anatomy and Neurobiology, 1-8 Yamadaoka Suita, Osaka 565-0871, Japan.
AJP Regulatory Integrative and Comparative Physiology (Impact Factor: 3.28). 10/2009; 298(1):R34-42. DOI: 10.1152/ajpregu.00205.2009
Source: PubMed

ABSTRACT Exaggerated jaw motor activities during sleep are associated with muscle symptoms in the jaw-closing rather than the jaw-opening muscles. The intrinsic activity of antagonistic jaw muscles during sleep remains unknown. This study aims to assess the balance of muscle activity between masseter (MA) and digastric (DG) muscles during sleep in guinea pigs. Electroencephalogram (EEG), electroocculogram, and electromyograms (EMGs) of dorsal neck, MA, and DG muscles were recorded with video during sleep-wake cycles. These variables were quantified for each 10-s epoch. The magnitude of muscle activity during sleep in relation to mean EMG activity of total wakefulness was up to three times higher for MA muscle than for DG muscle for nonrapid eye movement (NREM) and rapid-eye-movement (REM) sleep. Although the activity level of the two jaw muscles fluctuated during sleep, the ratio of activity level for each epoch was not proportional. Epochs with a high activity level for each muscle were associated with a decrease in deltaEEG power and/or an increase in heart rate in NREM sleep. However, this association with heart rate and activity levels was not observed in REM sleep. These results suggest that in guinea pigs, the magnitude of muscle activity for antagonistic jaw muscles is heterogeneously modulated during sleep, characterized by a high activity level in the jaw-closing muscle. Fluctuations in the activity are influenced by transient arousal levels in NREM sleep but, in REM sleep, the distinct controls may contribute to the fluctuation. The above intrinsic characteristics could underlie the exaggeration of jaw motor activities during sleep (e.g., sleep bruxism).

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    ABSTRACT: We aimed to characterize the association between jaw muscle contractions and respiratory events in patients with obstructive sleep apnea syndrome (OSAS) and to investigate the responsiveness of the contractions to respiratory events in comparison with that of leg muscles in terms of arousal types and sleep states. Polysomnographic (PSG) recordings were performed in 19 OSAS patients (F/M: 2/17; 53.1 ± 13.7 years; AHI: 31.8 ± 19.9/h) with no concomitant sleep bruxism or other sleep-related movement disorders. Muscle contractions of unilateral masseter (MAS) and anterior tibialis (AT) muscles were scored during sleep in association with graded arousals (microarousals and awakenings) related or unrelated to apneahypopnea events. Arousals were scored for 68.2% and 52.3% of respiratory events during light NREM and REM sleep, respectively. Respiratory events with arousals were associated with longer event duration and/or larger transient oxygen desaturation than those without (ANOVAs: p < 0.05). Median response rates of MAS events to respiratory events were 32.1% and 18.9% during NREM and REM sleep. During two sleep states, MAS muscle was rarely activated after respiratory events without arousals, while its response rate increased significantly in association with the duration of arousals (Friedman tests: p < 0.001). A similar response pattern was found for AT muscle. Motor responsiveness of the two muscles to arousals after respiratory events did not differ from responsiveness to spontaneous arousals in two sleep stages. In patients with OSAS, the contractions of MAS and AT muscles after respiratory events can be nonspecific motor phenomena, dependent on the duration of arousals rather than the occurrence of respiratory events. Kato T; Katase T; Yamashita S; Sugita H; Muraki H; Mikami A; Okura M; Ohi M; Masuda Y; Taniguchi M. Responsiveness of jaw motor activation to arousals during sleep in patients with obstructive sleep apnea syndrome. J Clin Sleep Med 2013;9(8):759-765.
    Journal of clinical sleep medicine: JCSM: official publication of the American Academy of Sleep Medicine 01/2013; 9(8):759-65. · 2.93 Impact Factor
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    ABSTRACT: BACKGROUND: To investigate the association between each clinical diagnosis criterion for sleep bruxism (SB) and the frequency of jaw motor events during sleep. METHODS: Video-polysomnography was performed on 17 healthy adult subjects (mean age, 26.7 ± 2.8 years), with at least one of the following clinical signs and symptoms of SB: (1) a report of frequent tooth grinding, (2) tooth attrition with dentine exposure through at least three occlusal surfaces, (3) morning masticatory muscle symptoms, and (4) masseter muscle hypertrophy. Episodes of rhythmic masticatory muscle activity (RMMA) and isolated tonic activity were scored visually. These variables were compared with regards to the presence or absence of each clinical sign and symptom. RESULTS: In 17 subjects, 4.0 ± 2.5/h (0.1-10.2) RMMA and 1.0 ± 0.8/h (0-2.4) isolated tonic episodes were observed (total episodes: 5.0 ± 2.4/h (1.2-11.6)). Subjects with self-reported grinding sounds (n = 7) exhibited significantly higher numbers of RMMA episodes (5.7 ± 2.3/h) than those without (n = 10; 2.8 ± 1.8/h) (p = 0.011). Similarly, subjects with tooth attrition (n = 6) showed significantly higher number of RMMA episodes (5.6 ± 3.1/h) than those without (n = 11; 3.2 ± 1.6/h) (p = 0.049). The occurrence of RMMA did not differ between the presence and absence of morning masticatory muscle symptoms or muscle hypertrophy. CONCLUSIONS: Clinical signs and symptoms frequently used for diagnosing SB can represent different clinical and physiological aspects of jaw motor activity during sleep.
    Sleep And Breathing 06/2013; · 2.26 Impact Factor
  • Progress in Brain Research - PROG BRAIN RES. 01/1998; 115:111-127.


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May 17, 2014