Swallow produces autonomic changes in a modified artificially perfused rat preparation

The autonomic nervous system is composed of the sympathetic and parasympathetic nervous systems which are important for cardiovascular, respiratory and ingestive coordination. The vagus nerve (X) is the main nerve carrying parasympathetic outflow affecting digestion, heart rate (HR), and the immune system; the vagus is also a key pathway for the entire swallow reflex. The maintenance of arterial pressure at adequate levels requires tonic sympathetic drive to control the contraction and the caliber of blood vessels, however the participation of the sympathetic drive during swallow behavior and any role it might play in swallow dysfunction have not been the subject of many studies. In this study, we are characterizing the contribution of the sympathetic nerve and any corresponding parasympathetic activity in rodents to assess its coordination with swallow and breathing, and the possible changes in heart rate and blood pressure. To achieve this aim, we utilized a modified non-paralyzed working heart-brainstem preparation of rats (P23-P28). Rather than transecting the animal, the spinal cord was left intact to obtain electrophysiological recordings of muscle activity from the diaphragm, submental and laryngeal complexes. Swallow was stimulated by infusing 0.1mL of water into the mouth before and after application of drugs. We observed a correlation between an increase of perfusion pressure during swallow stimulation and a decrease of heart rate. Under atenolol, a β-adrenergic blocker, spontaneous and evoked swallows still occurred but with no changes in heart rate. On the other hand, scopolamine, a nonselective muscarinic acetylcholine antagonist, prevented any changes in heart rate and perfusion pressure during swallow. We suggest that swallow triggers an excitatory vasomotor sympathetic pathway which is involved in the control of upper airway motor activity. Funded by NIH Grants: NS110169, HD110951 This abstract was presented at the American Physiology Summit 2025 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.