The K+-H+ exchanger, Nigericin, modulates taste cell pH and chorda tympani taste nerve responses to acidic stimuli

Abstract

The relationship between acidic pH, taste cell pHi, and chorda tympani (CT) nerve responses was investigated before and after incorporating the K+-H+ exchanger, nigericin, in the apical membrane of taste cells. CT responses were recorded in anesthetized rats in vivo, and changes in pHi were monitored in polarized fungiform taste cells in vitro. Under control conditions, stimulating the tongue with 0.15 M potassium phosphate (KP) or 0.15 M sodium phosphate (NaP) buffers of pHs between 8.0 and 4.6, KP or NaP buffers did not elicit a CT response. Post-nigericin (500 × 10-6 M), KP buffers, but not NaP buffers, induced CT responses at pHs ≤ 6.6. The effect of nigericin was reversed by the topical lingual application of carbonyl cyanide 3-chloro-phenylhydrazone, a protonophore. Post-nigericin (150 × 10-6 M), KP buffers induced a greater decrease in taste cell pHi relative to NaP buffers and to NaP and KP buffers under control conditions. A decrease in pHi to about 6.9 induced by KP buffers was sufficient to elicit a CT response. The results suggest that facilitating apical H+ entry via nigericin decreases taste cell pHi and demonstrates directly a strong correlation between pHi and the magnitude of the CT response. © The Author 2011. Published by Oxford University Press. All rights reserved.