Inactivation kinetics of Ca_{V}1.2 channels modulated by Ca_{V}*β* subunits and their mixtures. (*A*) Voltage dependence of the inactivation rate (determined as the fraction of peak current inactivated after 150 ms of depolarization) of Ca_{V}1.2/*α*_{2}*δ*1 coexpressed with Ca_{V}*β*_{1a} subunit (*up-pointing triangles*, *n* = 6), Ca_{V}*β*_{1a}Ca_{V}*β*_{2b} combination (2:1) (*solid circles*, *n* = 5), Ca_{V}*β*_{1a}Ca_{V}*β*_{2b} combination (1:1) (*solid diamonds*, *n* = 5), and Ca_{V}*β*_{2b} subunit (*down-pointing triangles*, *n* = 6), respectively. (*B*) Normalized representative Ba^{2+} currents through Ca_{V}1.2 channels traces evoked by 160 ms depolarization to +10 mV. (*C*) Percent of the current inactivation at 0.1-, 0.5-, 1-, and 5 s during 5-s test pulses to +10 mV. (*Open*, *light-shaded*, *medium-shaded*, and *solid bars*) Ca_{V}*β*_{1a} subunit (*n* = 5), Ca_{V}*β*_{1a}Ca_{V}*β*_{2b} combination (2:1) (*n* = 4), Ca_{V}*β*_{1a}Ca_{V}*β*_{2b} combination (1:1) (*n* = 4), and Ca_{V}*β*_{2b} subunit (*n* = 6) experiments, respectively. ^{∗}*p* < 0.05; †*p* < 0.01, one-way ANOVA followed by Dunnett's post-test compared with Ca_{V}1.2 channels containing Ca_{V}*β*_{2b} subunits. The apparent differences between the two mixtures of Ca_{V}*β*_{1a}Ca_{V}*β*_{2b} are not significant.

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