The chorda tympani (ChT) is a mixed nerve, branch of the facial nerve, crossing the middle ear and containing the preganglionic parasympathetic axons that innervate the sublingual and submandibular glands. The maintenance of a correct middle ear pressure (MEP) is essential for normal ear functions; its regulation has a sophisticated neural control mainly provided by middle ear receptors (tympanic plexus, TP) and Eustachian tube (ET). The information provided by chemoreceptors and baroreceptors of the TP is transmitted to the nuclei of the solitary tract (NST) and then a neural circuit promotes the activation of ET muscles. We hypothesize that the information provided by the TP may modulate submandibular and sublingual glands activity through a neural pathway involving the NST, the superior salivatory nucleus (SSN) and finally the ChT. According to our hypothesis, sudden perturbations of the MEP may stimulate saliva production with consequent swallowing, opening of the Eustachian tube and endotympanic pressure rebalancing.
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