Three types of voltage-dependent calcium currents in cultured human neuroblastoma cells.

The voltage-dependent calcium current (ICa) in cultured human neuroblastoma cells (NB-I) was studied by whole-cell recording. The low-threshold current (Il), the high-threshold, fast inactivating current (Ih.f.), and the high-threshold, slow inactivating current (Ih.s.) were identified. Il. was blocked by Ni2+. Ih.f. was blocked by omega-conotoxin GVIA. Ih.s. was blocked by nifedipine, and enhanced by Bay K 8644. These characteristics indicate that Il, Ih.f. and Ih.s. are consistent with the T-, N- and L-type ICa, respectively.