INFERIOR SALIVATORY NUCLEUS
We have already discussed one PREGANGLIONIC PARASYMPATHETIC (visceromotor nuclei) nucleus, the dorsal motor nucleus X. There are three other areas in the brain stem that contain preganglionic parasympathetic cell bodies. Unlike the dorsal motor nucleus X, these nuclei cannot be seen in your brain stem sections. The most caudal of these cell groups is the INFERIOR SALIVATORY nucleus of C.N. IX. This nucleus lies in the medulla just MEDIAL to the nucleus ambiguus. Preganglionic parasympathetic axons arising from cells in the inferior salivatory nucleus end within the OTIC GANGLION. Postganglionic axons then pass to the parotid gland where they stimulate secretion.
For our problem solving exercises you need to remember that the inferior salivatory nucleus lies medial to nucleus ambiguus in the medulla. Remember, the inferior salivatory nucleus is the visceromotor component of C.N. IX. Cells within this nucleus possess preganglionic parasympathetic axons that pass out of the brain stem just dorsal and lateral to the inferior olive and eventually synapse in the otic ganglion. A lesion involving the inferior salivatory nucleus will result in a loss of SALIVATION from the ipsilateral parotid gland.
ANYTIME IN THE PROBLEM SETS THAT THE LESION INVOLVES NUCLEUS AMBIGUUS AND THE AREA OF THE MEDULLA MEDIAL TO THE NUCLEUS AMBIGUUS, YOU MUST ASSUME THAT BOTH NUCLEUS AMBIGUUS AND THE INFERIOR SALIVATORY NUCLEUS ARE INVOLVED.
Keep in mind that a lesion of the inferior salivatory nucleus does not result in a complete loss of salivation because the opposite inf. sal. nuc. is OK and C.N. VII is OK. C.N. VII (via the Superior Salivatory Nucleus; to be discussed later) is involved in innervating the submandibular ganglion. Postganglionic neurons in this ganglion innervate the submandibular and sublingual glands (more on this later!).