Figure 5. Effect of nickel ions and amiloride on T-type Ca²⁺ current.

Dose-response curve for the block of T-type Ca²⁺ current by the antagonist. Data represent the average (± s.e.m.) responses from 9 and 7 cells at E16, for NiCl₂ and amiloride, respectively. The smooth curves represent the fit of the Hill equation to the data with IC₅₀= 5.4 and 156 μm and n_H= 0.88 and 0.98 for NiCl₂ and amiloride, respectively. Insets, typical responses to increasing concentrations of NiCl₂ and amiloride. Test pulses to −20 mV from a holding potential of −80 mV were delivered every 20 s. Traces shown here are control traces and current in presence of 1, 2, 5, 10, 20, 50, 100, 200 and 500 μm NiCl₂ or 5, 10, 20, 50, 100, 200, 500, 1000 and 5000 μm amiloride. Capacitance of the cells isolated from 16-day-old fetuses was 152 and 109 pF, respectively.