Diltiazem protects against neurotoxicity induced by excitotoxic amino acids on cochlear afferent fibers.

The neurotoxic effects of two glutamate agonists, kainic acid (KA) and monosodium glutamate (MSG), were analyzed in the pigmented rat cochlea. Neural damage occurring after KA or MSG treatments were evidenced by the presence of a majority of swollen fibers in the inner spiral bundle. The use of diltiazem (DI), a Ca2+ L-channel antagonist, to prevent cochlear neural damage induced by glutamate agonists resulted in a significant increase of unswollen afferent nerve fibers. MSG-treated animals, after DI pretreatment, recovered the normal latency of the compound action potential, and only unswollen nerve fibers were observed.