Submitted on May 30, 2003
Accepted on February 19, 2004
Preoptic hypothalamic warming suppresses laryngeal dilator activity during sleep
Dennis McGinty1*, Agnes Metes2, Md. Noor Alam1, David Megirian3, Darya Stewart4, and Ron Szymusiak5
1 Research Service, Veterans Administration, Greater Los Angeles Health System, Sepulveda, CA, USA; Department of Psychology, UCLA, Los Angeles, CA, USA
2 Research Service, Veterans Administration, Greater Los Angeles Health System, Sepulveda, CA, USA
3 Research Service, Veterans Administration, Greater Los Angeles Health System, Sepulveda, CA, USA; Division of Neuroscience, Australian National University, Canberra, Australia
4 Department of Psychology, UCLA, Los Angeles, CA, USA
5 Research Service, Veterans Administration, Greater Los Angeles Health System, Sepulveda, CA, USA; Department of Medicine, UCLA, Los Angeles, CA, USA
* To whom correspondence should be addressed. E-mail: dmcginty{at}ucla.edu.
Upper airway dilator activity during sleep appears to be diminished under conditions of enhanced sleep propensity such as following sleep deprivation, leading to worsening of obstructive sleep apnea. 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 to waking. Mild bilateral local POA warming (0.5-1.2 °C) significantly reduced IA, PA, and LT during NREM sleep, compared to a pre-warming NREM baseline. In some animals, effects of POA warming on PCA activity were found during waking or REM. Since 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 OSA patients.
