(R)-Roscovitine enhances VDI of channels containing L-DI. Inactivation was measured as the IPost/IPre ratio using the three-pulse protocol described in the legend to . Control (CNTL, gray circles), 100 μm (R)-roscovitine (R-Rosc, black squares), and washout (WO, gray triangles) data from −120 to peak inactivation were fitted using a single Boltzmann equation (smooth lines) to yield V½ and slope as described in the legend to . The activation-voltage relationship in control (right axis, open circles) is superimposed here for comparison with the voltage dependence of inactivation. The activation-voltage relationship was fitted by a single Boltzmann function (smooth lines), and the relationship was normalized to the maximum current from that fit. (R)-Roscovitine enhanced VDI of LLLL (A), LLNN (C), LLNL (E), LLLN (F), LN*LL (G), and LN*NN (H) channels but did not affect NNNN (B) and NLLL (D) channels. For LLLL channels (A), the Boltzmann parameters for inactivation were V½ = −19.6, −15.3, and −16.4; slope = −13.6, −19.1, and −18.7; maximum inactivation = 0.23, 0.67, and 0.27 for control, (R)-roscovitine, and washout, respectively, whereas those parameters for activation were V½ = 15.0 and slope = 15.6. For NNNN channels (B), the Boltzmann parameters for inactivation were V½ = −24.1, −24.7, and −28.6; slope = −13.9, −14.5, and −15.6; maximum inactivation = 0.48, 0.47, and 0.45 for control, (R)-roscovitine, and washout, respectively, whereas those for activation were V½ = 21.0 and slope = 12.6. For LLNN channels (C), the Boltzmann parameters for inactivation were V½ = 1.4, 0.8, and 0.6 mV; slope = −6.8, −10.0, and −5.0; maximum inactivation = 0.15, 0.6, and 0.15 for control, (R)-roscovitine, and washout, respectively, whereas those parameters for activation were V½ = −17.7 mV and slope = 9.6. It was not possible to accurately describe the inactivation data from the NLLL chimera (D) using the Boltzmann equation, but for activation, the Boltzmann parameters were V½ = 18.7 and slope = 21.7. For LLNL channels (E), the Boltzmann parameters for inactivation were V½ = −43.5, −51.8, and −45.8 mV; slope = −9.8, −13.3, and −9.5; maximum inactivation = 0.6, 0.81, and 0.58 for control, (R)-roscovitine, and washout, respectively, whereas those for activation were V½ = −9.2 mV and slope = 18.1. For LLLN channels (F), inactivation in control was too small to allow for Boltzmann fitting. However, the Boltzmann parameters for activation were V½ = 41.7 mV and slope = 19. For LN*LL channels (G), the Boltzmann parameters for inactivation were V½ = −79.1, −48.5, and −60.8 mV; slope = −9.1, −11.2, and −9.0; maximum inactivation = 0.07, 0.30, and 0.09 for control, (R)-roscovitine, and washout, respectively, whereas those parameters for activation were V½ = −21.7 mV and slope = 12.5. For LN*NN channels (H), the Boltzmann parameters for inactivation were V½ = −2.4, −12.1, and −2.5 mV; slope = −4.9, −5.2, and −7.1; maximum inactivation = 0.07, 0.29, and 0.09 for control, (R)-roscovitine, and washout, respectively, whereas those parameters for activation were V½ = 6.5 mV and slope = 11.6.