Neurons of the cochlear nucleus perform diverse information processing tasks. The stellate cells of the ventral cochlear nucleus (VCN) transform the irregular activity of their auditory nerve fiber inputs into a regular spike train output. However, stellate cells are a diverse population both morphologically and physiologically. In this proposal, we investigate some of the mechanisms that may be available to stellate cells to perform their specific information processing tasks. First, we will test the hypothesis that VCN stellate cells may differ among each other in their membrane conductances. In acutely isolated single cell preparations of identified stellate cells, we will characterize the voltage and ligand dependent ionic conductances present in the cell somatic membrane. We will focus on the characterization of transient outward currents and slowly developing outward and inward currents that may affect discharge regularity and rate adaptation, and on the biophysical characteristics of glycine and GABA receptors on the cell surface. Second, we will test the hypothesis that neurons of the dorsal cochlear nucleus provide one source of inhibitory input to VCN stellate cells. In brain slice preparations, we will intracellularly record, characterize, and identify by dye staining dorsal cochlear nucleus (DCN) cells that project to the VCN in a brain slice preparation. In conjunction with Project 2, we will attempt to identify the neurotransmitter used by these cells using immunocytochemistry on the identified cells. In addition, we will attempt to measure the influence of DCN cells that project to the VCN on identified VCN stellate cells using spike triggered averaging techniques. The design of these experiments is driven by observations made in in vivo preparations in Projects 2 and 4, and the results of these experiments will be used in the interpretation and specific design of experiments in those projects.
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