SUPERIOR LARYNGEAL NERVE-SECTION ALTERS RESPONSES TO UPPER AIRWAY DISTORTION IN SLEEPING DOGS

We investigated the effect of superior laryngeal nerve (SLN) section o n expiratory time (TE) and genioglossus electromyogram (EMGgg) respons es to upper airway (UA) negative pressure (UANP) in sleeping dogs. The same dogs used in a similar intact study (C. A. Harms, C. A., Y. -J. Zeng, C. A. Smith, E. H. Vidruk, and J. A. Dempsey. J. Appl. Physiol. 80: 1528-1539, 1996) were bilaterally SLN sectioned. After recovery, t he UA was isolated while the animal breathed through a tracheostomy. S quare waves of negative pressure were applied to the UA from below the larynx or from the mask (nares) at end expiration and held until the next inspiratory effort. Section of the SLN increased eupneic respirat ory frequency and minute ventilation. Relative to the same dogs before SLN section, sublaryngeal UANP caused less TE prolongation while acti vation of the genioglossus required less negative pressures. Mask UANP had no effect on TE or EMGgg activity We conclude that the SLN 1) is not obligatory for the reflex prolongation of TE and activation of EMG gg activity produced by UANP and 2) plays an important role in the mai ntenance of UA stability and the pattern of breathing in sleeping dogs .