Membrane properties of two types of basal cells in Necturus taste buds.

Necturus taste buds contain two types of basal cells: presumptive stem cells and Merkel-like basal cells. Both types of basal cells are small round cells located at the base of the taste bud, indistinguishable from each other with light microscopy. However, with electron microscopy, autoradiography, or immunocytochemistry, these two types of basal cells can be easily distinguished. We isolated basal cells from taste buds, characterized their voltage-dependent currents using gigaseal whole-cell recordings, and processed the cells for electron microscopy or immunocytochemistry. We were able to distinguish two cell types electrophysiologically and to correlate cell type with membrane properties. Isolated Merkel-like basal cells had several voltage-activated currents: transient, TTX-sensitive, inward Na+ current; sustained, saturating outward K+ current; and slowly inactivating inward Ca2+ current. These currents are similar to those observed in taste receptor cells. In contrast, presumptive stem cells from Necturus taste buds only had outward K+ currents.