SYMPATHETIC AND CGRP-POSITIVE NERVE SUPPLY TO THE ENDOLYMPHATIC SAC OF GUINEA-PIG

The distribution of sympathetic fibers and calcitonine gene related pe ptide (CGRP)-positive fibers was examine in endolymphatic sac of 10 gu inea pigs by using immunohistochemical techniques to demonstrate tyros ine hydroxylase (TH) and CGRP. A meshwork of TH-positive fibers, found around the sigmoid sinus, sent branches to the distal and the interme diate parts of the endolymphatic sac. In these areas. TH-positive fibe rs traveled freely from blood vessels and formed a loose plexus beneat h the lining epithelium. Such fibers were rare in the proximal portion of the endolymphatic sac and in the endolymphatic duct. Seven days af ter elimination of the ipsilateral superior cervical ganglion, some of the TH-positive fibers were gone, however, there were still a few fib ers in the endolymphatic sac as well as around the sigmoid sinus, thus their origin remains obscure. CGRP-positive fibers also branched from the fibers around the sigmoid sinus, and were distributed throughout the endolymphatic sac, some occasionally extending to the endolymphati c duct. They not only formed a dense plexus in the sublining space, bu t also spread through the lining cell layer. Elimination of the ipsila teral superior cervical ganglion did not affect the distribution of CG RP-positive fibers, indicating that they are probably not sympathetic fibers.