We characterized a voltage-dependent ionic current in dental pulp cells on dental pulp slices using a nystatin perforated-patch recording configuration. The outward currents in dental pulp cells were inhibited by the following channel blockers: 1) Ca(2+)-free extracellular solution containing 10 mM Ba2+, 2) extracellular 400 nM apamin and 3) extracellular 300 nM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). On the other hand, 15 mM tetraethylammonium (TEA) did not inhibit the outward currents. The inhibitory effects of Ca(2+)-free extracellular solution, apamin and DIDS had voltage-dependency. These results indicated that dental pulp cells expressed a small-conductance Ca(2+)-activated K+ current (SK current) and a DIDS-sensitive Cl- current. The functional significance of these channels is discussed.