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COMPLEX FUNCTION OF THE CENTRAL NERVOUS SYSTEM, SLEEP AND LOCOMOTION

Preoptic hypothalamic warming suppresses laryngeal dilator activity during sleep

¹Veterans Administration, Greater Los Angeles Health System, Sepulveda 91343; Departments of ²Psychology and ⁴Medicine, University of California-Los Angeles, Los Angeles, California 90095; and ³Division of Neuroscience, Australian National University, Canberra 2600, Australia

Submitted 30 May 2003 ; accepted in final form 19 February 2004

Upper airway dilator activity during sleep appears to be diminished under conditions of enhanced sleep propensity, such as after sleep deprivation, leading to worsening of obstructive sleep apnea (OSA). Non-rapid eye movement (NREM) sleep propensity originates in sleep-active neurons of the preoptic area (POA) of the hypothalamus and is facilitated by activation of POA warm-sensitive neurons (WSNs). We hypothesized that activation of WSNs by local POA warming would inhibit activity of the posterior cricoarytenoid (PCA) muscle, an airway dilator, during NREM sleep. In chronically prepared unrestrained cats, the PCA exhibited inspiratory bursts in approximate synchrony with inspiratory diaphragmatic activity during waking, NREM, and REM. Integrated inspiratory PCA activity (IA), peak activity (PA), and the lead time (LT) of the onset of inspiratory activity in PCA relative to diaphragm were significantly reduced in NREM sleep and further reduced during REM sleep compared with waking. Mild bilateral local POA warming (0.5–1.2°C) significantly reduced IA, PA, and LT during NREM sleep compared with a prewarming NREM baseline. In some animals, effects of POA warming on PCA activity were found during waking or REM. Because POA WSN activity is increased during spontaneous NREM sleep and regulates sleep propensity, we hypothesize that this activation contributes to reduction of airway dilator activity in patients with OSA.

non-rapid eye movement sleep; laryngeal airway dilator; preoptic hypothalamus; warm-sensitive neurons; posterior cricoarytenoid; obstructive sleep apnea