This project is to provide new knowledge of how the cochlear nucleus processes information coming from the organ of hearing through the auditory nerve. Small mammals have been used in these studies. A highly specific antibody against GABA, used by us for immunocytochemistry, has given us excellent visualization of GABAergic terminals in light microscopy studies. This antibody tolerates high levels of glutaraldehyde and ultrastructure is beautifully maintained in the EM studies. Furthermore, our use of an antibody against the glycine receptor allows the visualization and identification of glycinergic synapses in the auditory system. We have shown that both the cochlear nucleus and superior olivary complex have large and complex GABA and glycinergic inputs. We have used antisera against glutaminase and aspartate aminotransferase in immunocytochemical studies to try and define how excitatory amino acid neurons may be immunocytochemically marked. We have found that glutaminase is enriched in many such neurons but not all, while aspartate aminotransferase is enriched in only a few of these neurons. We have determined on tissue slice preparations that the auditory nerve postsynaptic receptor in chickens is of the kainate type, and in mammals it is of the NMDA type. We have biochemical studies in progress of axonally transported proteins in the auditory nerve, concentrating on two groups of proteins, the rapidly transported proteins (RTPs) and a group of proteins whose expression is changed after hair cell loss. This study relates to the critical issue that the success of cochlear prostheses is dependent on a functioning auditory nerve.
