Localization of laryngeal muscle motoneurons in rat

Abstract

Medullar localization of laryngeal motoneurons has been studied in rat using horseradish peroxidase (HRP) as a retrograde tracer.After enzyme injection in laryngeal muscles labelled neurons were found in the nucleus ambiguus (NA) from 0.5 mm caudal to 1.5 mm rostral to the obex.The presence of labelled cells in both NA after sectioning of left recurrent laryngeal nerve showed the existence of a contralateral projection from NA motoneurons.HRP labelled cells were spindle-shaped and multipolar, NA laryngeal motoneurons were located in a well defined columnar arrangement parallel to the middle line.Motoneurons that innervate pharyngeal and soft palate muscles were located in the anterior part of NA up to the caudal end of the nucleus facialis.