Fig. 4.

P1018L inactivation is not affected by changes in [Ca²⁺]_i. (A–C) Time course of WT and P1018L current development elicited by 300 μM ADPR with different concentrations of [Ca²⁺]_i. Shown are average currents (±SEM) measured at −80 and +80 mV. I/V curves, taken at the peak in representative cells and plotted (Right), show P1018L (solid lines) and WT (broken lines) currents reversing close to 0 mV. P1018L inactivated at all [Ca²⁺]_I, e.g., 10 nM (WT, n = 17; P1018L, n = 9), 250 nM (WT, n = 10; P1018L, n = 7), and 1 μM (WT, n = 13; P1018L, n = 8). (D) Dose–response plots of peak current amplitudes (I_max) and activation rates (t_{1/2 Imax}) at different [Ca²⁺]_i. I_max stayed relatively constant across [Ca²⁺]_i concentrations for both WT and P1018L (Left). Activation was faster as [Ca²⁺]_i levels increased (Right). The I_max and t_{1/2 Imax} are not significantly different in WT and P1018L. (E) P1018L decay is not influenced by [Ca²⁺]_i. Averaged current decay traces ± SEM (Left) and t_{1/2 decay} (Right). The number of P1018L cells averaged for the [Ca²⁺]_I concentrations not previously listed are as follows: 50 nM, n = 10; 100 nM, n = 10; not buffered, n = 16.