IMMUNOCYTOCHEMICAL LOCALIZATION OF ASPARTATE AND GLUTAMATE IN THE PERIPHERAL VESTIBULAR SYSTEM

Controversy exists concerning the identity of the neurotransmitter in the mammalian peripheral vestibular system. Several candidates have be en proposed, including the excitatory amino acids glutamate and aspart ate and the inhibitory amino acid gamma-aminobutyric acid (GABA). Prev ious studies have demonstrated vestibulonerual electrophysiological ac tivity associated with glutamate and aspartate. Paraffin sections of r at vestibular ganglia and end-organs were examined for the presence of glutamate-like and aspartate-like immunoreactivity. Our results demon strate the presence of both aspartate-like and glutamate-like immunore activity in vestibular hair cells, peripheral vestibular nerve fibers, and vestibular ganglion cells. Minimal immunoreactivity was noted in the tissues surrounding these cells. These data add support to the hyp othesis that the excitatory amino acids glutamate and aspartate are in volved in vestibular neurotransmission.