POTASSIUM CHANNELS IN AUDITORY TEMPORAL PROCESSING

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Although some information about auditory stimuli such as sound frequency is encoded by the spatial pattern of active neurons, many aspects of the stimulus such as the intensity, pitch and localization are largely encoded by the temporal discharge patterns of neurons in auditory circuits. The timing and rate at which a neuron fires is largely determined by the types and amounts ionic conductances it possesses. In particular, recent studies have emphasized the role of voltage-dependent potassium channels in shaping the responses of different brainstem auditory neurons to a sound stimulus. The genes for a large number of K+ channels have now been isolated, and their electrophysiological properties investigated by expression in Xenopus oocytes and non-excitable cell lines. We have identified by in situ hybridization and immunohistochemistry, one type of K+ channel, the Show Kv3.1, channel which is particularly enriched in a subset of auditory neurons. The relationship of these Kv3.1 channels to the currents that have been recorded in real auditory neurons has not been established. However, our ongoing modeling studies have suggested that these channels may be important for preserving the timing of rapid synaptic inputs. The goal of this proposal is to establish the functional role of Kv3.1 channels in auditory neurons. EM immunohistochemistry will be used to examine the exact subcellular distribution of Kv3.1 channels in auditory neurons, and whether this is the same for neurons with differing patterns of synaptic input. In addition, immunological techniques will be used to identify other K+ channel subunits which may heteroligermize with Kv3.1 proteins. To determine the contribution of the Kv3.1 channel to outward currents of auditory neurons, electrophysiological measurements will be made to rigorously compare currents in auditory neurons with Kv3.1 currents expressed alone or with other K+ channel subunits in cell lines. This comparison will also be made in situations where the level of Kv3.1 expression is selectively altered to further verify the Kv3.1 components. Finally, hybrid arrest techniques and/or gene knockout will be used to directly assess the involvement of kv3.1 channels in regulating the timing of action potentials in individual auditory neurons. These studies should provide information on the mechanisms involved in determining the characterized firing patterns of certain auditory neurons and may advance the understanding of the underlying physiology involved in processing of rapid auditory information.