Identifying the fundamental importance of excitatory neurons within the caudal Nucleus of the Solitary Tract in swallow production

Oropharyngeal dysphagia is a remarkable commonality in most pulmonary, sleep, and neurological disorders and exacerbates underlying conditions increasing the frequency of hospitalizations. Recently it was determined that the postinspiratory complex (PiCo) triggers swallow in a respiratory phase dependent manner, however the swallow pattern generator (SPG) is historically thought to be located within the Nucleus of the Solitary Tract (NTS). This led to a conclusion that PiCo aids in regulating swallow-breathing coordination, but the cell-type specific neurons responsible for swallow generation remains unknown. We hypothesize excitatory neurons within the cNTS are necessary for swallow generation. Using both male and female Vglut2cre mice, either a cre-dependent ChR2 or DREADD AAV was bilaterally injected into the interstitial (SolI) and intermediate (SolIM) portion of the nucleus of the solitary tract (cNTS) to either active or silence these neurons. Twenty-one days after injection, using our freely breathing urethane anesthetized mouse model, swallows were stimulated by 1) injection of water into the oral cavity or 2) optogenetic stimulation of cNTS neurons; before and after DREADD activator, clozapine-N-oxide (CNO). Swallow and laryngeal activity were measured via monopolar suction electrodes of the hypoglossal (XII) and vagus (X) nerves as well as bipolar electromyogram (EMG) of the submental, laryngeal complex and costal diaphragm muscles. Post-hoc histological analysis was done to confirm areas of interest were targeted. We found that activation of Vglut2 neurons in the cNTS triggers a swallow, while silencing these neurons inhibited swallow production when orally given water. We propose that excitatory cNTS neurons are a part of the SPG and are necessary for swallow production. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.