The objective is to understand the role of taste cell renewal in the aging process. Food identification difficulties and a lack of proper nutrition have been noted in the elderly. The role of taste in these deficiencies is not understood. A likely physiological change in taste for the elderly is a slowing down of taste cell renewal. The relationship between taste perception and taste cell renewal is not known. The specific aims are: (1) Compare taste cell renewal in young and old Fischer-344 rats. (2) Simultaneously, the functioning of the taste system of young and old rats will be studies to note any decrease in sensitivity with age, using a comprehensive analysis of behavior in the presence of a variety of tastants and by electrophysiological recordings from peripheral taste nerves, including those from the palate. (3) Finally, changes in taste bud renewal will be experimentally introduced by injecting vinblastine sulfate, which arrests mitosis in its metaphase and by injecting testosterone, which alters the life cycle of the taste cells. The effects of these changes will be measured both by recording the neural changes in the taste nerves and by thoroughly studying the taste behavior of the rat.