The vertebrate taste bud is a good model for studying cellular aging in the nervous system. Taste cells possess many characteristics shared by neurons, such as excitability, chemosensitivity, and synapses (Roper, 1983a; Kinnamon, Taylor, Delay and Roper, 1985; Kinnamon and Roper, 1986). Taste cells have the added advantage that their lifespan is short (only a few days) compared to neurons, and thus age-related changes can be measured with reliability and confidence: complicating factors such as metabolic or hormonal differences between young and old animals are avoided. Furthermore, detailed analyses of age- related changes in the biophysical properties of taste cells and in their membrane chemosensitivity can be conducted on taste cells. Taste cells from the mudpuppy (Necturus maculosus) will be impaled with microelectrodes in situ, using a new isolated preparation developed in this laboratory (Roper, 1983). In depth analyses of the membrane conductances, particularly potassium conductance, will shed light on how ionic channels change over the lifespan of an excitable cell. Chemical stimuli will be applied focally onto the apical surface of taste cells to sutdy what age- related changes in chemosensitivity occur. Cells will be impaled with dye-filled micropipettes to identify the cells in subsequent light and electron micrographs in order to correlate the functional properites of the cell with its age: recent observations have indicated that taste cell aging can be determined by ultrastructural features (Kinnamon, et al. 1985; Delay, Kinnamon and Roper, 1986). These findings will provide information on cellular aging in excitable tissues and will also lead to a better understanding of taste transduction mechanisms.
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