In the neonatal hamster the cells and afferent inputs in the dorsal cochlear nucleus mature simultaneously; the major goal of this proposal is to determine how the development of the fusiform cells and their inputs are related. The methods and specific aims can be summarized as follows: 1) Using horseradish peroxidase, individual cochlear nerve axons will be filled and their images reconstructed to study the development of the topographic organization of the fibers. 2) The development of topographic organization of the fusiform cells in normal animals and those deprived of cochlear input will be studied using Golgi methods. 3) By administering a drug that depletes granule cells, one of the major inputs to the fusiform cells, the role of the granule cell input in the development of the fusiform cells will be studied. 4) The development of GAD-immunoreactive input to the fusiform cells will be investigated with immunohistochemical methods and electron microscopy. The precise relationships that exist between axons and their target neurons presumably play important roles in determining the connectivity within a nucleus. The experiments outlined in this proposal will further our understanding of how these relationships develop under normal circumstances and how they are sometimes disrupted in circumstances similar to those that exist in deafened or developmentally-impaired animals.
