<p><i>Aa</i>, Schematic of the P/-8 voltage protocol. <i>Ab</i>, Representative current at full scale, which is expanded in panel <i>Ac</i>. <i>B,C</i> Representative gating current traces recorded during depolarizing voltage steps from −100 to ∼ +50 mV (reversal potential): WT Ca<sub>v</sub>3.1 (<i>Ba</i>); GD1–2 (<i>Bb</i>); GD3–5 (<i>Bc</i>); WT Ca<sub>v</sub>3.3 (<i>Ca</i>); ID1–2 (<i>Cb</i>); and ID3–5 (<i>Cc</i>). Vertical scale bar is same size for all six traces (0.1 nA), while the horizontal scale bar is 1 ms in <i>B</i> and 2 ms in <i>C</i>. Data were acquired at 20 kHz, filtered at 10 kHz, and represent the average of 20 runs. G<sub>max</sub> vs. Q<sub>max</sub> for WT Ca<sub>v</sub>3.1 and GD1–2 (<i>D</i>), or WT Ca<sub>v</sub>3.3 and ID1–2 (<i>E</i>). The slope of the linear regression fit provides an estimate of <i>P<sub>o</sub>,</i> and in both cases the slope of the line fitting the D1–2 mutants was 2-fold higher than for WT (Ca<sub>v</sub>3.1, 0.26±0.03, n = 9; GD1–2, 0.55±0.06, n = 6, P<0.001; Ca<sub>v</sub>3.3, 0.12±0.01, n = 9; and ID1–2, 0.26±0.02, n = 6, P<0.05). The difference between Ca<sub>v</sub>3.1 and Ca<sub>v</sub>3.3 is also statistically significant (P<0.001, one-way ANOVA followed by Tukey's multiple comparison test, Prism).</p
