Fig. 5.

The FHM-1 R192Q mutation also promotes recovery from G-protein inhibition. a Representative normalized current traces elicited at 0 mV (left panel) and 20 mV (right panel) before (I_Control) and under 10 μM DAMGO application (I_DAMGO) for Ca_v2.1^R192Q/β₄/α₂δ-1_b channels (top panel). Corresponding traces allowing the measurement of the maximal DAMGO inhibition at the start of the depolarisation (GI_t0) (bottom panel). The arrow indicates the start of the depolarisation. Scale: 50 ms. b Bar chart representation of GI_t0 for Ca_v2.1^R192Q/β₄/α₂δ-1_b channels (n = 11) as a function of membrane potential. c Shift of the current time to peak induced by DAMGO application for Ca_v2.1^R192Q/β₄/α₂δ-1_b channels (n = 11) as a function of membrane potential. d Normalized I_{G-protein unbinding} traces at 0 mV (left panel) and 20 mV (right panel) fitted by a mono-exponential decrease (red dashed line) allowing the determination of the time constant τ of current recovery from G-protein inhibition (top panel). The arrow indicates the start of the depolarisation. Traces that allowed the measurements of RI value (in red) are also shown (bottom panel). e Time constant τ of recovery from G-protein inhibition as a function of membrane potential for Ca_v2.1^R192Q/β₄/α₂δ-1_b channels (n = 11). f Bar chart representation of RI values for Ca_v2.1^R192Q/β₄/α₂δ-1_b channels (n = 11) measured after 200 ms depolarization as a function of membrane potential. Data are presented as mean ± S.E.M for n studied cells. The dotted line shows position of values for Ca_v2.1 wild-type channels. Statistical t test: *, p ≤ 0.05, **, p ≤ 0.01; ***, p ≤ 0.001.