Key result
Rat study reveals the vagus nerve provides redundant carotid baroreceptors and chemoreceptors alongside glossopharyngeal nerves.
Why the study?
The vagal pathway to carotid baro- and chemoreceptors and the glossopharyngeal intracranial afferent/sensory pathway connecting to the brainstem had not been identified.
This anatomical tracing study demonstrates that the vagus nerve provides redundant innervation to carotid baro- and chemoreceptors alongside the glossopharyngeal nerve in rats.
Rat vagal redundancy data should not alter clinical baroreflex practice; extends rodent anatomy and leaves open human translation.
The glossopharyngeal nerve, via the carotid sinus nerve (CSN), presents baroreceptors from the internal carotid artery (ICA) and chemoreceptors from the carotid body. Although neurons in the nodose ganglion were labelled after injecting tracer into the carotid body, the vagal pathway to these baro- and chemoreceptors has not been identified. Neither has the glossopharyngeal intracranial afferent/sensory pathway that connects to the brainstem been defined. We investigated both of these issues in male Sprague-Dawley rats (n = 40) by injecting neural tracer wheat germ agglutinin-horseradish peroxidase into: (i) the peripheral glossopharyngeal or vagal nerve trunk with or without the intracranial glossopharyngeal rootlet being rhizotomized; or (ii) the nucleus of the solitary tract right after dorsal and ventral intracranial glossopharyngeal rootlets were dissected. By examining whole-mount tissues and brainstem sections, we verified that only the most rostral rootlet connects to the glossopharyngeal nerve and usually four caudal rootlets connect to the vagus nerve. Furthermore, vagal branches may: (i) join the CSN originating from the pharyngeal nerve base, caudal nodose ganglion, and rostral or caudal superior laryngeal nerve; or (ii) connect directly to nerve endings in the middle segment of the ICA or to chemoreceptors in the carotid body. The aortic depressor nerve always presents and bifurcates from either the rostral or the caudal part of the superior laryngeal nerve. The vagus nerve seemingly provides redundant carotid baro- and chemoreceptors to work with the glossopharyngeal nerve. These innervations confer more extensive roles on the vagus nerve in regulating body energy that is supplied by the cardiovascular, pulmonary and digestive systems.
No takes yet. Share an insight, caveat, or question.
Wang et al. (2019) studied Anatomy of vagal baro- and chemoreceptors (n=40). Neural tracer wheat germ agglutinin-horseradish peroxidase injection was evaluated on Identification of vagal and glossopharyngeal pathways to baro- and chemoreceptors. Neural tracer injection in 40 male rats revealed that the vagus nerve provides redundant carotid baro- and chemoreceptors to work with the glossopharyngeal nerve.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: