Fig. 3.

Ca²⁺ influx through L-type calcium channels affects the repolarization phase. A₁: representative threshold APs in the absence or presence of 10 μM nifedipine (Nif) in β₄KO neurons. A₂: representative threshold APs in the absence or presence of 5 μM Pax in addition to 10 μM Nif. B: Nif increased the 10% width of threshold AP in β₄KO neurons. Averaged 10% width in ms: control 1.77 ± 0.04 (n = 24); Pax 2.20 ± 0.12 (n = 8); Nif 2.05 ± 0.04 (n = 11); Nif/Pax 2.32 ± 0.10 (n = 15). Nif and control are significantly different (P ≈ 0.0005). Nif/Pax and Nif are significantly different (P ≈ 0.04). Nif/Pax and Pax are not significantly different (P ≈ 0.46). C: Nif did not reduce the fAHP amplitudes of threshold AP in β₄KO neurons. Averaged fAHP amplitudes in mV: control −14.7 ± 0.6 (n = 24); Pax −10.6 ± 0.9 (n = 8); Nif −13.5 ± 1.0 (n = 11); Pax/Nif −8.4 ± 1.0 (n = 15). Nif and control are not significantly different (P ≈ 0.28). Pax/Nif and Pax are not significantly different (P ≈ 0.19). Nif/Pax and Nif are significantly different (P ≈ 0.003). *P < 0.05.