Sympathetic innervation in the larynx of cats

Abstract

The site of origins, peripheral courses and intramucosal distribution of the sympathetic post-ganglionic nerve fibers supplying to the larynx were investigated by means of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) and Falck-Hillarp method in 51 cats. The cervical sympathetic ganglia which send the postganglionic fibers to the larynx were the superior cervical ganglion (SCG), middle cervical ganglion (MCG), and stellate ganglion (SG). Location of MCG was at the bifurcation of the cervical sympathetic trunk, rostrally to the point of its crossing with the subclavian artery. After WGA-HRP injection, labeled sympathetic nerve fibers were observed mainly in the wall of the blood vessels and around the laryngeal glands of the posterior and caudal parts of the larynx. Labeled fibers originated from SCG were seen in the mucosa of the arytenoid region and posterior glottis ipsilaterally. Both the internal and external branches of the superior and inferior laryngeal nerves contained the postganglionic fibers from SCG. Labeled nerve fibers from MCG were recognized in the ipsilateral mucosa of the glottis and subglottis and were also contained in the internal and external branches of the superior and the inferior laryngeal nerves. Labeled sympathetic nerve fibers from SG appeared in the mucosa caudal to the first tracheal ring. The pattern of distribution of labeled sympathetic nerve fibers revealed by WGA-HRP technique coincided with that of the noradrenergic fibers stained by Falck-Hillarp method.