Fig. 7.

Effect of heterologous overexpression of wild-type and mutant Gβ4 on GIRK channel activation. Time course of basal and NE-activated GIRK1 and GIRK4 channel currents in wild-type β4γ4- (A), β4(80)γ4- (B), and β4(55,88,89)γ4-expressing neurons. Currents were evoked by 200 msec voltage ramps from −140 to −40 mV from a holding potential of −60 mV applied every 10 sec. Filled bars indicate application of 10 μm NE or 1 mm Ba²⁺ and 10 μm NE.Insets show current traces obtained before (a) and after (b) application of NE or NE plus Ba²⁺(c). D, Box plot showing the 10th, 25th, 50th (median), 75th, and 90th percentiles of peak GIRK currents before (Basal) and after (NE-activated) external application of 10 μm NE. Both the 10th and 90th percentiles are denoted byshorter lines. Numbers in parentheses indicate the number of experiments.