Vagal control of larynx resistance to the air flow

Abstract

Air flow larynx resistance changes have been recorded in dogs after electrical stimulation and lesion of the recurrent and vagus cervicalis nerves respectively. Experiments were carried out with glottis in situ and isolated. The effects of the administration of athropine i.v. (0.3 mg/kg) were also studied. Air flow larynx resistance decreased after secting the right recurrent nerves as well as after athropine administration. Electrical stimulation of the central end of the right vagus nerve produced a complex response characterized by an initial apnaea followed by a larynx resistance decrease. After a few seconds the response continued with glottis spasms followed by typical emetic movements. During the emetic movements larynx closed and opened throughout the respiratory cycle, the closing movement being simultaneous with the inspiratory position of the thorax and with minimal values of the intraabdominal pressure. Larynx resistance increased after uni- and bilateral sections of the vagus cervicalis and after the electrical stimulation of the peripheral end of the right vagus cervicalis. According to the present results, the possible existence of a controlling reflex of laryngeal sphincter motility, generated at the bronchopulmonary level, is postulated.