Respiratory-related pharyngeal constrictor muscle activity in decerebrate cats

Kuna, Samuel T., and Christi R. Vanoye.Respiratory-related pharyngeal constrictor muscle activity indecerebrate cats. J. Appl. Physiol.83(5): 1588-1594, 1997.Respiratory-related activity of thehyopharyngeus (middle pharyngeal constrictor) and thyropharyngeus(inferior pharyngeal constrictor) muscles was determined indecerebrate, tracheotomized adult cats and compared with theelectromyographic activity of the thyroarytenoid, a vocal cordadductor. During quiet breathing, the hyopharyngeus and usually thethyroarytenoid exhibited phasic activity during expiration and tonicactivity throughout the respiratory cycle. Respiratory-related thyropharyngeus activity was absent under these conditions. Progressive hyperoxic hypercapnia and progressive isocapnic hypoxia increased phasic expiratory activity in both pharyngeal constrictor (PC) musclesbut tended to suppress thyroarytenoid activity. Passively inducedhypocapnia and the central apnea that followed the cessation of themechanical hyperventilation were associated with tonic activation ofthe hyopharyngeus and thyroarytenoid but no recruitment inthyropharyngeus activity. The expiratory phase of a sigh and progressive pneumothorax were associated with an increase in phasic thyroarytenoid activity but no change in phasic PC activity. The results indicate that a variety of stimuli modulate respiratory-related PC activity, suggesting that the PC muscles may have a role in theregulation of upper airway patency during respiration.