Fits of Scheme 2+2′ to WT and V2 reactivation kinetics. (*A*) Scheme 2+2′ accounts for WT and V2's reactivation time courses after hyperpolarizations of various amplitudes *V*_{h} (between −53 and −193 mV) and duration *t*_{h}. Test voltages were +37 and +67 mV for WT and V2, respectively. All of the displayed data come from the same WT and V2 patch recordings and correspond to the following *t*_{h} values. WT: for *V*_{h} = −113 mV, *t*_{h} = 0.5, 0.7, 1, and 2 ms; for *V*_{h} = −153 mV, *t*_{h} = 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, and 1 ms; for *V*_{h} = −193 mV, *t*_{h} = 0.1, 0.2, 0.3, 0.4, and 0.6 ms. V2: for *V*_{h} = −53 mV, *t*_{h} = 0.2, 0.5, 1, 2, and 5 ms; for *V*_{h} = −53 mV, *t*_{h} = 0.1, 0.2, 0.5, 1, and 5 ms. In the simulations, for WT, *a*_{1} and *a*_{2} were each increased by 20% compared with the values in Table , and the values for β_{N-1}(0) and β_{N}(0) were 520 and 280 s^{−1}. For V2, β_{N }was changed to 1,100 s^{−1}. Data are from patches w448 and v162. (*B*) Scheme 2+2′ accounts for the delay δ_{a} in WT and V2's reactivation time course for different *V*_{h} and *t*_{h}. The δ_{a} values were derived from the measured and simulated currents from *A*. (*C* and *D*) WT's reactivation time courses were used to place constraints on the sizes of *q*_{b1} and *q*_{b2}. For reactivation time courses measured after *V*_{h} = −193 mV, values for *q*_{b1} and *q*_{b2 }that are two or three times as large as the values in Table predict a reactivation delay that is too long. In *D*, the three superimposed lines to the left of the squares reflect δ_{a} values derived from simulated currents for the *q*_{b1} and *q*_{b2 }values in Table (the best fit) or *q*_{b1} and *q*_{b2 }values that are two or three times larger. For these simulations, the values of *b*_{1}(0) and *b*_{2}(0) were first adjusted to achieve good fits of WT's reactivation time course for *V*_{h} = −113 mV (shown by the derived δ_{a} values in *D*).

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