Localization of the NO/cGMP-pathway in the cochlea of guinea pigs

The presence of nitric oxide synthase (NOS) in substructures of the cochlea of guinea pigs is an issue of current focus. Moreover, information concern ing the localization of cells effected by the NO/GMP-pathway are rare. Para ffin sections of guinea pig cochlea were incubated with specific antibodies to the three known NOS isoforms, soluble guanylyl cyclase (sGC) and cyclic guanosine monophosphate (cGMP), the second messenger system of NO. While d etection of inducible iNOS failed in all cochlear structures, expression of endothelial eNOS was found in the spiral ligament, in the stria vascularis , in cells of the organ of Corti, in nerve fibers and in some perikaryia of the spiral ganglion. The cochlear nerve showed an accentuated affinity for immunostaining in distal, basal segments of the cochlea. Neuronal bNOS was found predominantly in the endosteum of the modiolus and cochlea and was l ess intensively present in all perikaryia of the spiral ganglion and in the spiral ligament. Supporting cells of the organ of Corti and cells in the l imbus spiralis displayed only modest immunostaining, while bNOS was not fou nd in outer and inner hair cells. NOS detection was accompanied by immunore activity to sGC and to cGMP. The presence of NOS and its second messenger s ystem gives evidence for a possible involvement in neurotransmission, regul ation of the cochlear amplifier and in homeostasis. (C) 1999 Elsevier Scien ce B.V. All rights reserved.