Gating and patterning of sequential swallowing by brainstem loci in the juvenile in situ rat (1178.10)

Abstract

During swallowing, aspiration of ingested material is prevented by laryngeal adduction of the vocal folds. The Kölliker‐Fuse nucleus (KF) is known to provide pre‐motor drive to laryngeal adductor motoneurons while the nucleus of the solitary tract NTS is the designated swallowing centre of the brainstem. This study investigated the roles of the KF and NTS in the gating and patterning of sequential swallowing in the in situ perfused brainstem‐spinal cord preparation of rat. Oral injection of water evoked fast sequential swallowing in situ. Inhibition of KF resulted in an increased incidence of spontaneous swallowing and loss of swallowing‐related tonic laryngeal adduction, but did not significantly alter swallowing activity per se. Disinhibition of KF resulted in exaggerated tonic activity and delayed swallows. Our results indicate that KF contributes to the gating of swallowing activity and simultaneously mediates a separate reflex identity (pharyngo‐glottal reflex) that adducts the upper airway during sequential swallowing. The latter is critical for preventing penetration of the lower airways. Finally, GABA receptor activation/blockade of NTS reveals that the: (i) the NTS circuitry is essential for generation of rhythmic swallowing in situ, and; (ii) generation of sequential swallowing depends on fast synaptic inhibition.Grant Funding Source: ARC