Electrophysiological identification of mouse taste bud cells

Taste buds, biological chemical sensors, consist of four types of taste bud cells (Types I to IV TBCs) classified morphologically or immunohistochemically. Since both morphological and immunohistochemical classification essentially require the fixation of TBCs, the physiological properties of classified cells are completely destroyed. We have developed a physiological classification, typically for Type II cells, taste receptor cells, as well as for Type III cells, the only one cell type that has synaptic contacts with taste nerve fibers, based on voltage-gated currents of TBCs. Here we show that the magnitude of outward rectifier currents was much larger in Type II and III cells than in Type I cells, and that the main component of the outward rectifier currents was TEA-insensitive Cl− channel currents in Type II cells but TEA-sensitive K+ channel currents in Type III cells. These results enable us to apply protocols appropriate to elucidate the physiological role of each cell type in taste reception.