EFFECTS OF DL-ALPHA-AMINOADIPATE ON SYNAPTICALLY AND CHEMICALLY EVOKED EXCITATION OF ANTEROVENTRAL COCHLEAR NUCLEUS NEURONS OF THE CAT

This paper reports the effects of iontophoretically applied glutamate, aspartate, kainate, N-methyl-d-aspartate and acetylcholine on single units in the antero-ventral cochlear nucleus of pentobarbital anesthetized cats. In addition, the effects of dl-α-aminoadipate, a dicarboxylic amino acid antagonist, on chemically induced and synaptically evoked excitation on these units are described. The manner in which units responded to iontophoretically applied compounds was not dependent on their characteristic frequency or response pattern. Single units could be separated according to their waveform as prepotential and non-prepotential. Non-prepotential units responded to iontophoretically applied excitants in a manner similar to units in other regions of the CNS. The actions of the amino acids were antagonized by dl-α-aminoadipate but the synaptic excitation of the units was rarely affected by this antagonist. Prepotential units normally either did not respond or showed depolarization block to the excitants. dl-α-aminoadipate readily blocked the synaptic excitation of these units. The results are discussed with reference to the anatomy of cells in the antero-ventral cochlear nucleus and their primary afferent innervation. The results support the supposition that either glutamate or aspartate (or both) is the primary afferent transmitter of the auditory nerve. © 1979.