Fig. 5.

Specific inhibition of noninactivating and T-type currents by nifedipine and TTA-P2. Ca²⁺ channel currents were activated by 300-ms (A–E) or 10-ms (F) voltage steps from a holding potential of −80 mV at 30-s intervals. Cells were superfused with nifedipine or TTA-P2 alone or in combination. A and B: block of rapidly (A) or slowly (B) activating noninactivating L-type currents by nifedipine. Numbers (1 and 2) on traces (left) correspond to those on plot of current amplitudes (right). C and D: block of T-type and rapidly (D) or slowly (C) activating noninactivating Ca²⁺ currents by TTA-P2 (2 or 3 μM), followed by TTA-P2 + nifedipine (Nifed, 1 μM). E: block of L- and T-type currents by nifedipine (1 μM), followed by nifedipine + TTA-P2 (2 μM). F: block of deactivating T-type current by TTA-P2, but not nifedipine. Deactivating T-type current was recorded in response to 10-ms depolarizing steps. Cell was superfused with nifedipine (1 μM), followed by TTA-P2 (1 μM). Numbers (1, 2, and 3) on traces (left) correspond to those on plot of “tail” current amplitudes (right).