Localization of motoneurons innervating the Eustachian tube muscles in cat

The localizations of the motoneurons supplying the tensor tympani muscle (TTM), tensor veli palatini muscle (TVPM) and levator veli palatini muscle (LVPM) were determined by retrograde transport of horseradish peroxidase (HRP) in the cat. TTM motoneurons were found ipsilaterally outside the trigeminal motor nucleus in an area just ventral to it. TVPM motoneurons were distributed mainly in the ventral part of the ipsilateral trigeminal motor nucleus. They were more compactly distributed in the rostral part of the nucleus than in the caudal part. LVPM motoneurons were found in the ipsilateral nucleus ambiguus. There were no HRP-labelled cells in the contralateral nucleus ambiguus.