• Maria Clotilde Carra, Guido M Macaluso, Pierre H Rompré, Nelly Huynh, Liborio Parrino, Mario Giovanni Terzano, and Gilles J Lavigne.
• Faculté de Médecine Dentaire, Université de Montréal, and Centre d'étude du Sommeil et des Rythmes Biologiques, Hôpital du Sacré-Coeur de Montréal, Québec, Canada.
• Sleep. 2010 Dec 1;33(12):1711-6.

Study ObjectiveClonidine disrupts the NREM/REM sleep cycle and reduces the incidence of rhythmic masticatory muscle activity (RMMA) characteristic of sleep bruxism (SB). RMMA/SB is associated with brief and transient sleep arousals. This study investigates the effect of clonidine on the cyclic alternating pattern (CAP) in order to explore the role of cyclic arousal fluctuation in RMMA/SB.DesignPolysomnographic recordings from a pharmacological study.SettingUniversity sleep research laboratory.Participants And InterventionsSixteen SB subjects received a single dose of clonidine or placebo at bedtime in a crossover design.Measurements And ResultsSleep variables and RMMA/SB index were evaluated. CAP was scored to assess arousal instability between sleep-maintaining processes (phase A1) and stronger arousal processes (phases A2 and A3). Paired t-tests, ANOVAs, and cross-correlations were performed. Under clonidine, CAP time, and particularly the number of A3 phases, increased (P≤0.01). RMMA/SB onset was time correlated with phases A2 and A3 for both placebo and clonidine nights (P≤0.004). However, under clonidine, this positive correlation began up to 40 min before the RMMA/SB episode.ConclusionsCAP phase A3 frequency increased under clonidine, but paradoxically, RMMA/SB decreased. RMMA/SB was associated with and facilitated in CAP phase A2 and A3 rhythms. However, SB generation could be influenced by other factors besides sleep arousal pressure. NREM/REM ultradian cyclic arousal fluctuations may be required for RMMA/SB onset.

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