Kynurenic acid and gamma-D-glutamylaminomethylsulfonic acid suppress the compound action potential of the auditory nerve.

Kynurenic acid and gamma-D-glutamylaminomethylsulfonic acid, two excitatory amino acid antagonists, were perfused through the guinea pig cochlea while monitoring various cochlear potentials. Both drugs (0.6-10 mM) reduced the magnitude of the compound action potential (CAP) of the cochlear nerve without much effect on other potentials. The results are consistent with the hypothesis that the hair cell transmitter is an excitatory amino acid, possibly L-glutamate.