UPPER AIRWAY MOTOR OUTPUTS DURING VOMITING VERSUS SWALLOWING IN THE DECEREBRATE CAT

Swallowing and vomiting are antagonistic motor acts; nevertheless, vom iting can be immediately followed by swallowing. The purpose of this s tudy was to clarify the interrelationship between these two behaviors, particularly in regard to comparing the upper airway motor patterns a t the end of the expulsion phase with those during subsequent swallowi ng. Experiments were conducted using both paralyzed and non-paralyzed decerebrate cats, in which recordings were obtained either from upper airway muscles, the diaphragm and abdominal muscles or from the nerves that innervate those muscles. The activity patterns of most nerves re corded in paralyzed animals were consistent with the behavior recorded in non-paralyzed animals from the muscles innervated by those nerves, with the exception of the cricothyroid and stylopharyngeus muscles. V omiting can be divided into a series of retches followed by expulsion, which itself can be further subdivided into three phases. The final s tage of expulsion, characterized by burst-like exaggerated activity of the laryngeal elevator thyrohyoid and the pharyngeal constrictors, pr oved to be different from pharyngeal swallowing, as judged from differ ences in the spatio-temporal patterns of the upper airway motor output s. However, post-vomiting swallowing activity was still observed even after total deafferentation of the laryngeal and pharyngeal areas in p aralyzed animals. It is therefore likely that the central processes fo r vomiting and swallowing closely relate in generating these two behav iors. (C) 1998 Elsevier Science B.V.