Action of glutamate in the cat labyrinth.

Glutamate solutions of either 50 mM applied on the membranous labyrinth or 1 mM perfused into the lateral canal in cats increased spontaneous and stimulus-evoked activity of vestibular neurons. Kainic acid (10(-4) M) perfused into the labyrinth produced a depolarizing action on vestibular afferents. These results indicate that glutamate could be an excitatory neurotransmitter at the synapse between vestibular hair cells and afferent nerve fibers in the cat.