**(***R*)-Roscovitine enhances VDI of channels containing L-DI. Inactivation was measured as the *I*_{Post}/*I*_{Pre} 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 *V*½ 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 *V*½ = −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 *V*½ = 15.0 and slope = 15.6. For NNNN channels (*B*), the Boltzmann parameters for inactivation were *V*½ = −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 *V*½ = 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 *V*½ = −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 *V*½ = 18.7 and slope = 21.7. For LLNL channels (*E*), the Boltzmann parameters for inactivation were *V*½ = −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 *V*½ = −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 *V*½ = 41.7 mV and slope = 19. For LN*LL channels (*G*), the Boltzmann parameters for inactivation were *V*½ = −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 *V*½ = −21.7 mV and slope = 12.5. For LN*NN channels (*H*), the Boltzmann parameters for inactivation were *V*½ = −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 *V*½ = 6.5 mV and slope = 11.6.

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