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

Voltage-dependent calcium currents (ICa), which developed in cultured human neuroblastoma cells (NB-I), were studied using a whole-cell recording technique. Three types (T-, N- and L-type) of ICa were identified based on their biological and pharmacological properties. The T-type ICa was observed in about 60% of the cells from day 2 to day 12 and in about 20% after day 14. Likewise, the amplitude gradually decreased from -61.7 +/- 10.1 pA on day 2 to -18.3 +/- 9.1 pA on day 18. The N-type ICa appeared on day 6, with the number of cells exhibiting this current increasing up to 90.9% (-73.4 +/- 16.0 pA) on day 14 and immediately decreasing thereafter. The L-type ICa was observed in 50.0% of the cells on day 2, increasing to 84.6% of the cells on day 6 and remaining thereafter, while the amplitude gradually increased from -37.8 +/- 14.0 pA on day 2 to -158.8 +/- 22.8 pA on day 18, and decreased thereafter. These findings indicate that the expression of the voltage-dependent Ca2+ channels is strongly regulated by the developmental stage of the cell.