Keywords: ASICs, acid-sensing ion channels; [Ca2+]o, extracellular Ca2+ concentration; DEG/ENaC, degenerin/epithelial Na+ channel; DiI, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchloride; IpH6.0, pH 6.0-induced currents; pH1/2, pH for half-maximal a