Immunohistochemical studies on the guinea pig's vestibular ganglion cell--with reference to the distribution of substance P and neurofilament

Abstract

The immunocytochemical distribution and morphological characteristics of substance P and neurofilament in vestibular end organs and the vestibular ganglion of the guinea pig were investigated. The effect of capsaicin on substance P-like immunoreactivity was also evaluated in this study. Substance P-like immunoreactivity was found in the peripheral region of vestibular end organs and in small or medium size vestibular ganglion cells. Approximately 85% of vestibular ganglion cells showed substance P-like immunoreactivity. Although substance P-like immunoreactivity was depleted in the nasal mucosa and trigeminal ganglion by capsaicin treatment, substance P distributed in the primary vestibular neurons was not affected. In contrast to the distribution of substance P, neurofilament was also found in the primary afferent neurons in the central regions of vestibular end organs. Neurofilament immunoreactive cells, which were larger in size than cells without neurofilament-like immunoreactivity comprised about 34% of vestibular ganglion cells. These immunocytochemical findings suggest that vestibular ganglion cells can be classified on the basis of size and immunocytochemical characteristics.