REGENERATED TASTE BUDS AND SALT TASTE RESPONSES IN THE RAT CHORDA TYMPANI NERVE

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After chorda tympani nerve (CT) transection, taste buds degenerate and disappear. Given time, however, taste buds reappear in fungiform papillae after regeneration of the cut nerve. In the present study, recovery of Na salts response from the regenerated CT after unilateral transection of the chorda tympanilingual nerve in the adult rats was investigated using amiloride, a sodium ion channel blocker. Taste responses from the regenerated CT were first obtained 28 days after transection of the nerve. Ratios for all responses were calculated relative to the 0.5 M NH_4CI response. The relative magnitude of the responses to 0.3-0.5 M NaCl and Na acetate from the regenerated CT were about 0.6 on days 28-35, and were about 0.8 on days 36-45. Results of amiloride treatment revealed that amiloride-sensitive components in the regenerated CT was small on days 28-35 and abruptly increase thereafter. However, amiloride-insensitive components were not related to times after transection of the nerve, when the magnitude of the responses to Na salts was expressed relative to that to 0.5 M NH_4Cl. La ions, a tight junction blocker, at 2.5 mM did not affect amilorideinsensitive components in both the regenerated CT in surgery rats and the intact CT in control rats. This suggests that paracellular pathways between taste cells are not involved in amiloride-insensitive sodium taste reception in the rat.