Fig. 3

T-type Ca²⁺ currents. a Voltage sequence. Test pulses (100 ms, −80 up to −20 mV in 10-mV increments), preceded by a 2-s prepulse of −100 mV to fully deactivate the T-type channels, were applied at 0.1 Hz. b–d Representative current traces; the capacitative and leak currents were not subtracted in (b) and (c). The T-type Ca²⁺ channel blocker Ni²⁺ (100 μM) blocks the inward currents (c), suggesting the presence of T-type currents, based on the difference currents (d) between the control currents (b) and currents with Ni²⁺ (c). The inactivation time constant was determined by exponential fitting as shown in (d). e Variation of inactivation time constant with command voltage. Data represent means ± SEM. Upper or lower error bars are shown for clarity. (The voltages are not corrected for liquid junction potential in this figure or in Figs. 4–6)