Influence of intrathoracic vagotomy on the cough reflex in the anesthetized cat

Recurrent laryngeal afferent fibers are primarily responsible for cough in response to mechanical or chemical stimulation of the upper trachea and larynx in the guinea pig. Lower airway slowly adapting receptors have been proposed to have a permissive effect on the cough reflex. We hypothesized that vagotomy below the recurrent laryngeal nerve branch would depress mechanically or chemically induced cough. In anesthetized, bilaterally thoracotomized, artificially ventilated cats, thoracic vagotomy nearly eliminated cough induced by mechanical stimulation of the intrathoracic airway, significantly depressed mechanically stimulated laryngeal cough, and eliminated capsaicin-induced cough. These results support an important role of lower airway sensory feedback in the production of tracheobronchial and laryngeal cough in the cat. Further, at least some of this feedback is due to excitation from pulmonary volume-sensitive sensory receptors.