THE AFFERENT ACTIVITY OF THE SUPERIOR LARYNGEAL NERVE, AND RESPIRATORY REFLEXES SPECIFICALLY RESPONDING TO INTRALARYNGEAL PRESSURE CHANGES IN ANESTHETIZED SHIBA GOATS

This study was aimed at characterizing the superior laryngeal nerve (S LN) afferent activities under four different respiratory conditions, i .e., tracheostomy breathing (TB), upper airway breathing (UAB), trache al occlusion (TO) and upper airway occlusion (UAO), and investigating respiratory changes in response to transmural pressures applied to the larynx in anesthetized Shiba goats. The activity recorded from the wh ole SLN increased at both inspiration and expiration during TB, UAB an d TO, while an expiratory augmentation accompanied by an inspiratory i nhibition was found during UAO. Based on recordings from 109 thin fila ment-preparations, 47 units were identified as 'drive' receptors, 31 a s 'pressure' receptors (22 'positive' and 9 'negative' pressure recept ors), and the rest 31 as 'non-modulated type' of receptors. The poster ior cricoarytenoid (PCA) muscle activity showed a clear inspiratory mo dulation during UAB and was significantly enhanced by negative pressur e applied to the isolated upper airway, where such an augmented activi ty was abolished by bilateral section of the SLN. No significant chang es were found in the respiratory cycle during application of negative pressures to the larynx. The respiratory modulation of the SLN in Shib a goats was essentially identical to that reported for rabbits, rats a nd guinea pigs, but not in dogs. The reflex response of the upper airw ay muscles to the laryngeal pressure changes in Shiba goats were found to be,less noticeable than in rabbits and dogs.