Motor neurons of the laryngeal nerves.

The present study was undertaken to determine the relationship between the motor neurons of the superior and recurrent laryngeal nerves within the nucleus ambiguus. The retrograde transport of horseradish peroxidase was utilized to identify the motor neurons subsequent to its application to the proximal transected end of the superior and recurrent laryngeal nerves. Labeled superior laryngeal motor neurons were distributed ventrolaterally in the rostral portion the nucleus. The recurrent laryngeal motor neurons were distributed throughout the nucleus with two distinct populations: a rostral group and a caudal group. The rostral group overlaps the motor neurons of the superior laryngeal nerve. The caudal group occupies that portion of the nucleus that is classically described for the recurrent laryngeal nerve. Additional superior laryngeal nerve labeled perikarya were found in the dorsal motor nucleus of the vagus. This study defines the rostral distribution of the recurrent laryngeal nerve motor neurons and suggests that this rostral group is a component of the neuroanatomical substrate that is involved in the co-activation of the laryngeal abductors controlling the laryngeal aperture.