Differential effects of βARK-ct on M₁R- and Dr-VSP–induced inhibition of Ca_V2.2(β2a) currents. (A) Ca_V2.2(β2a) current inhibition by Dr-VSP activation in control or cells expressing βARK-ct. Cells received a 10-ms test pulse (a) and then a 1-s depolarization to 120 mV for activating the expressed VSP, followed by the second 10-ms test pulse (b). Note that current inhibition by Dr-VSP activation was not significantly different between control and βARK-ct–expressing cells. (B) Summary of the current inhibition (percentage) after the activation of M₁ receptors (Fig. 2 A) or Dr-VSP in control and βARK-ct–expressing cells. Data are mean ± SEM (n = 5–7).