Localization of laryngeal motoneurons in the rat: Morphologic evidence for dual innervation?

Abstract

The distribution in the brain stem of neurons supplying the laryngeal muscles cricothyroid (CT), posterior cricoarytenoid (PCA), and thyroarytenoid-lateral cricoarytenoid (TA-LCA) was investigated in the rat. Horseradish peroxidase (HRP) was injected into individual muscles and applied to the cut end of the cervical vagus, the superior laryngeal nerve, and the recurrent laryngeal nerves. The CT was represented rostrally and ventrolaterally to nucleus ambiguus. The PCA was represented in the middle of NA but not in a ventral or dorsal lamina. The TA-LCA overlapped the representation of PCA. Two cell types were labeled by both intramuscular injection and application of HRP to the cut end of nerves. Smaller cells were located in a dorsal lamina of nucleus ambiguus. Evidence is presented that these cell types are equivalent to the two types supplying laryngeal muscles from two separate nuclei in other species.