Role of intrinsic muscles and tracheal motion in modulating laryngeal receptors.

Recording from the superior laryngeal nerve discloses a respiratory modulated activity even in the absence of airflow and pressure changes in the larynx. The present study evaluates the relative contribution of intrinsic laryngeal muscle activity and transmitted tracheal movement on the respiratory modulation of laryngeal mechanoreceptors. Seventy-four receptors were studied in 22 anesthetized spontaneously breathing dogs. The modulation of 31 receptors depended solely on laryngeal muscle activity since it was abolished by cold block of laryngeal nerves. Twelve receptors were primarily activated by tracheal movement since tracheal stabilization alone reduced or abolished their modulation. The respiratory modulation of the remaining 31 receptors was found to be dependent on both laryngeal muscle activity and tracheal movements. Lidocaine (2%) was applied to the receptor field of 13 endings; the results indicate that while some receptors are located superficially (blocked within 1 min) others are located in deeper structures (not affected in 30 min). These receptors may be involved in the precise coordination of laryngeal muscle activity and could play a role in the regulation of breathing pattern and airway patency due to their pressure sensitivity.