Immunohistochemical and electrophysiological demonstration of substance P in human vestibular ganglion cells.

This study was performed in order to determine the immunohistochemical expression and distribution pattern as well as the electrophysiological actions of substance P in human vestibular ganglion cells. Substance P-like immunostaining was mainly found in the cytoplasm of small vestibular ganglion cells. In contrast, nerve fibers were not labeled. Using intracellular recording techniques, substance P produced a slow depolarization of membrane potentials accompanied by an increase in membrane resistance. Furthermore, an enhanced firing response to depolarization occurred.