Sympathetic Nervous System in Guinea Pig Cochlea

Abstract

The cochlear sympathetic nerve supply in hearthy guinea pigs was studied by immunohistochemical demonstration of tyrosine hydroxylase (TH) and dopamine B-hydroxylase (DBH). The cochlear sympathetic nerve fibers originated in the ipsilateral superior cervical ganglion and reached the Schwann-glial border of the cochlear nerve via the labyrinthine artery. Some of these fibers ran among the cochlear nerve fibers to go directly to the osseous spiral lamina and others enrered the intraganglionic spiral bundle to head toward the osseous spiral lamina of the upper turn. Along their course, sympathetic fibers came close to the nodes of Ranvier of type I neurons and acetylcholinesterase-positive unmyelinated fibers in the intraganglionic spiral bundle. Most of the fibers finally ended adjacent to blood vessels, especially around the tympanic lip vessels. These fibers were rarely observed at the habenula perforata and in the organ of Corti.