Acid-induced responses in hamster chorda tympani and intracellular pH tracking by taste receptor cells

HCl- and NaCl-induced hamster chorda tympani nerve responseswere recorded during voltage clamp of the lingual receptive field. Voltage perturbations did not influence responses to HCl. In contrast, responses to NaCl were decreased by submucosal-positive and increased by submucosal-negative voltage clamp. Responses to HCl were insensitive to the Na⁺ channel blockers,amiloride and benzamil, and to methylisobutylamiloride (MIA), anNa⁺/H⁺exchange blocker. Responses to NaCl were unaffected by MIA but weresuppressed by benzamil. Microfluorometric and imaging techniques wereused to monitor the relationship between external pH(pH_o) and the intracellular pH(pH_i) of fungiform papilla tastereceptor cells (TRCs) following2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein loading.TRC pH_i responded rapidly andmonotonically to changes in pH_o.This response was unaffected byNa⁺ removal or the presence ofamiloride, benzamil, or MIA. The neural records and the data fromisolated TRCs suggest that the principal transduction pathway for acidtaste in hamster is similar to that in rat. This may involve themonitoring of changes in TRC pH_i mediated through amiloride-insensitiveH⁺ transport across TRC membranes.This is an example of cell monitoring of environmental pH through pHtracking, i.e., a linear change inpH_i in response to a change inpH_o, as has been proposed for carotid bodies. In taste, the H⁺transport sites may be concentrated on the basolateral membranes ofTRCs and, therefore, are responsive to an attenuatedH⁺ concentration from diffusion ofacids across the tight junctions.