Kinetic assays reveal participation of Gβγ in M₁ receptor–induced Ca_V2.2(β2a) current inhibition. (A) Summary of Fig. 4 B. The estimated effect of M₁R-mediated release of Gβγ on Ca_V2.2 current (ΔCa_V2.2, green) was calculated by subtracting the mean current of βARK-ct (orange) from that of control (red). Blue trace indicates M₁R-induced PIP₂ hydrolysis observed by FRET change. (B) Interpretation of the Ca_V2.2 current inhibition as a series of exponential curves in control and βARK-ct–expressing cells. I_control = exp(−t/4.05) (t > 0; red), I_βARK-ct = 0.52*exp(−(t − 4)/4.87) (t > 4; orange), FRET_r = exp(−(t − 4)/8.78) (t > 4; blue). Predicted Gβγ-induced Ca_V current inhibition (dashed green) was calculated by subtracting the mean current of βARK-ct from that of control. The amplitude of I_βARK-ct is determined by obtaining the relative current amplitude between control and βARK-ct–expressing cells.