Expression of inducible nitric oxide-synthase in the vestibular system of hydropic guinea pigs

Immunohistochemical investigations of the guinea pig vestibular system, using a specific antibody to the inducible isoform of NO-synthase (iNOS/NOS II), have been performed 3 weeks after surgical closure of the right endolymphatic duct (n = 7). Endolymphatic hydrops (ELH) of the right temporal bone became evident by excavation of the Reissner's membrane in all seven animals. Those animals revealed iNOS-expression in ganglion cells, in the wall of blood vessels and in nerve fibers of the right vestibular system, while the corresponding left temporal bones and temporal bones of non-operated controls (n = 6) as well as of sham-operated animals (n = 3) did not show any iNOS-positive structures. iNOS-generated NO could be involved in the pathophysiology of vestibular dysfunction in Meniere's disease.