Cellular changes in fungiform papillae from mammalian tongue resulting from degeneration and subsequent regeneration of the chorda tympani nerve bundle (CT) will be measured. We propose and will test a hypothesis that predicts that upon transection of the CT the initial degeneration (and subsequent regeneration) of the taste buds is correlated with the ability of the epithelial cells to maintain (or lose) their intercellular contacts (i.e., tight junctions, desmosomes, gap junctions). Epithelial transport measurements for different tastants and elicited responses from the CT will be used to demonstrate that unilateral transection of the CT has pronounced effects on both the ipsilateral and contralateral sides of the tongue. After unilateral CT transection epithelial responses to salts (NaCl, KCl), saccharides (sucrose, D- glucose), acid (HCL) and a bitter tastants will be measured as a function of time to determine if the transport pathways for different tastants are expressed at the same or different times. Cellular processes involved in taste transduction will be elicited by measuring the transport pathways for ions and nonelectrolytes through isolated dog and rat tongue. Patrticular emphasis will be placed on characterizing the entry and exit pathways for ions that are activated by the presence of various salts and sweet and bitter tastants under a range of ionic conditions. The saccharide stimulated, amiloride inhibitable transport pathway will be studied in detail by obtaining its ion selectivity as well as salt and voltage dependence. The effects of c-AMP on the stimulation of transport by bitter tastants, caffeine and quinine will be studied on regions of tongue having fungiform and/or circumvallate papillae.
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