Ion Channels Contributing to the Generation of Salt-Induced Response in Isolated Bullfrog Taste Cells

Abstract

The contribution of the transduction pathway on the basolateral [1] and the receptive membranes [2] to the mechanism underlying the generation of the receptor potential induced by salt stimuli has been suggested individually by different groups. In previous studies, we reexamined the transduction mechanism of salt stimuli by changing the superficial and interstitial fluid of the frog tongue separately, using the lingual artery perfusion method [3, 4]. Three important results were obtained: (1) the magnitude of the receptor potentials decreased by 50% after the removal of Na⁺ and Ca²⁺ from interstitial fluid; (2) the reversal potential of salt-induced responses altered depending on the types and concentrations of salt stimuli after removal of Na⁺ and Ca²⁺ from both the superficial and interstitial fluid; and (3) substitution of an organic anion for Cl⁻ and application of a Cl⁻ channel blocker changed the reversal potential of salt response. These results led us to the conclusion that at least three types of ion channels, non-selective cation channels, K⁺ channels, and Cl⁻ channels, on the receptive membrane, and a Na⁺ conductive pathway activated by an unknown second messenger on the basolateral membrane contribute to salt-induced responses in frog taste cells.