Laryngeal and tracheal afferent nerve stimulation evokes swallowing in anaesthetized guinea pigs

center dot Activation of vagal afferent nerves innervating the tracheal and laryngeal mucosa evokes swallowing in anaesthetized guinea pigs. center dot The swallowing evoked by airway stimulation was probably initiated by the activation of the same afferent nerves that regulate coughing but occurred at lower stimulus intensities and was less susceptible to desensitization than the cough reflex. center dot We speculate that the swallowing associated with airway sensory nerve activation is a key component of airways protection from aspiration. Abstract We describe swallowing reflexes evoked by laryngeal and tracheal vagal afferent nerve stimulation in anaesthetized guinea pigs. The swallowing reflexes evoked by laryngeal citric acid challenges were abolished by recurrent laryngeal nerve (RLN) transection and mimicked by electrical stimulation of the central cut ends of an RLN. By contrast, the number of swallows evoked by upper airway/pharyngeal distensions was not significantly reduced by RLN transection but they were virtually abolished by superior laryngeal nerve transection. Laryngeal citric acid-evoked swallowing was mimicked by laryngeal capsaicin challenges, implicating transient receptor potential vanilloid 1 (TRPV1)-expressing laryngeal afferent nerves arising from the jugular ganglia. The swallowing evoked by citric acid and capsaicin and evoked by electrical stimulation of either the tracheal or the laryngeal mucosa occurred at stimulation intensities that were typically subthreshold for evoking cough in these animals. Swallowing evoked by airway afferent nerve stimulation also desensitized at a much slower rate than cough. We speculate that swallowing is an essential component of airway protection from aspiration associated with laryngeal and tracheal afferent nerve activation.