New insights into a decerebrate feline model of swallow‐breathing coordination

Abstract

In the medulla, the swallow and respiratory central pattern generators (CPGs) interact to coordinate swallow initiation and permit swallow execution during the expiratory phase of breathing. Disruption of swallow‐breathing coordination can result in dysphagia, which is a major cause of morbidity and mortality in many neuro‐muscular diseases, especially stroke. Despite extensive study, the precise mechanisms of swallow‐breathing coordination are not known. We tested the hypothesis that both central inspiratory activity and vagal feedback from the lungs are key elements for effective swallow‐breathing coordination. Swallows were triggered by electrical stimulation of the superior laryngeal nerves (SLN) or by injection of water into the pharyngeal cavity in decerebrate, paralyzed and artificially ventilated cats while motor activities were recorded from phrenic, hypoglossal, lumbar and vagal nerves. Mechanical ventilation was either triggered by central inspiratory activity or set independently from the phrenic activity to alter the timing of bronchopulmonary vagal afferent input and allow analysis of its influence on swallow‐breathing coordination. We observed two types of swallows that produced opposite effects on central respiratory‐rhythm resetting across all conditions: post‐Inspiratory type swallows disrupted central I activity without affecting expiration, whereas expiratory type swallows prolonged expiration without affecting central inspiratory activity. Repetitive swallows observed during apnea reset the E2 phase of central respiration and produced facilitation of swallow motor output. Moreover, swallow initiation was negatively modulated by vagal feedback and was reset by lung inflation. Collectively, these findings support a reciprocal inhibition between central inspiration and the swallow CPG and they are consistent with a role for pulmonary stretch receptors in the coordination between brainstem CPGs for breathing and swallowing. They may also prove relevant for healthcare management of dysphagia.Support or Funding InformationOT2OD023854‐01, HL109025This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.