Immunolocalization of orphanin FQ in rat cochlea.

Orphanin FQ/nociceptin (OFQ/N) and its receptor (ORL-1) have been proposed to play a role in the regulation of hearing. In this study, we investigate the localization of OFQ/N-like immunoreactivity in the mammalian cochlea. Sprague-Dawley rat temporal bones were harvested and decalcified. The organ of Corti was microdissected, and indirect immunohistochemistry was performed using a rabbit polyclonal antibody raised against OFQ/N. Immunoreactivity was seen in the tunnel crossing fibers and the large boutons terminating onto outer hair cells, and in the fibers terminating onto the afferents to the inner hair cells. The findings are consistent with OFQ/N expression in lateral and medial olivocochlear efferents.