Immunocytochemical localization of mitochondrial and cytosolic aspartate aminotransferase isozymes in the vestibular end-organs of rats.

The localization of mitochondrial (m-) and cytosolic (c-) aspartate aminotransferase (AAT) was examined in the vestibular ganglion neurons and sensory cells in the vestibular end-organs of rats by an indirect immunohistochemical method using antibodies specific for m- and c-AAT. Neurons in the vestibular ganglion were stained by both m- and c-AAT antibodies, but the vestibular sensory cells exhibited only m-AAT-like immunoreactivity and were not labeled by c-AAT. These findings suggested that aspartate is a neurotransmitter in the hair cells of the vestibular end-organs.