The localization of motoneurons innervating the canine pharyngeal constrictor muscles in the posterior larynx by the fluorescent double-labeling technique.

The localization of motoneurons innervating the canine pharyngeal constrictor muscles in the posterior larynx, i.e., the hyopharyngeal muscle (HP), the thyropharyngeal muscle (TP) and the cricopharyngeal muscle (CP), was investigated by the fluorescent labeling technique. Labeled cells were found in the rostral portion of the ipsilateral nucleus ambiguus. The rostral ends of these cell columns were located at nearly the same level. The caudal ends of the HP cell column and the TP cell column were also located at nearly the same level. However, the CP cell column was elongated a little more caudally. The HP cells and the TP cells were intermingled in the dorsal part of the nucleus. The CP cells were mainly located in the ventral part of the nucleus. No double-labeled cells were detected.