Effects of L-aspartate and oxaloacetic acid on click-evoked cochlear potentials.

The scala tympani of the guinea pig was perfused with artificial perilymph and experimental solutions using an electrical micropump. In test perfusions, 20 mM L-aspartate produced depression of APN1 by 49% and 25 mM L-aspartate decreased the amplitude of APN1 by 42%. Both 20 mM and 25 mM L-aspartate were without effect on the CM, the latency or width of APN1. Perfusions with 10 mM oxaloacetic acid were without effect on the APN1 and CM. In our previous experiments, 5 mM L-aspartate had no effect on APN1 and CM, but 10 mM L-aspartate or 15 mM L-aspartate introduced into the scala tympani reversibly increased the amplitude of APN1 and CM. It is concluded that L-aspartate may have a modulating influence on signal transmission of afferent synapses in the cochlea.