Acid and salt responses in mouse taste cells

Acid and salt responses of taste cells induced by natural stimulation have not been investigated with exception of early studies with conventional mic roelectrode method, due to the toxicity of high concentration of salt or lo w pH of acid stimuli applied to isolated taste cells. This indicates that t he application of rapid and localized stimulation to the apical membrane of taste cells is necessary for recording of natural responses to salt or aci d stimuli using patch clamp technique. Recently we have developed a procedu re to accomplish the quasi-natural condition including rapid, localized sti muli to the apical receptive membrane and the maintenance of taste bud pola rity. In this review, we present our recent results obtained under quasi-na tural condition using patch clamp techniques, comparing with the previously proposed hypothesis. One of our major finding is the fact that the acid-in duced responses of taste cells in the mouse fungiform papillae are never su ppressed by amiloride but an apical proton-gated conductance and a basolate ral Cl- conductance possibly contribute to sour transduction. On the other hand, salt-induced responses are suppressed by amiloride, although the salt -induced responses recorded from a single cell involve both amiloride-sensi tive and -insensitive components. Furthermore, the amiloride-insensitive co mponent of salt responses possibly consists of multiple subcomponents inclu ding an apical sodium-gated nonselective cation conductance and a basolater al Cl- conductance. Recent reports also support the hypothesis that both ac id and salt responses require specific receptor mechanisms of inorganic cat ions such as H+ and Na+ at the apical receptive membrane. (C) 2000 Elsevier Science Ltd. All rights reserved.