Figure 5.

β₂-adrenergic facilitation of GIRK currents is not produced by coupling to inhibitory G-proteins. (A) Original current traces recorded at −80 mV. GIRK currents were induced by superfusion of the oocytes with 1 μmol/liter isoproterenol. (Top) Current trace from an oocyte expressing β₂AR^wt and treated with PTX. (Bottom) Same as in the top, but the oocyte expressed β₂AR ^PF instead of β₂AR^wt. (B) Statistics of the effect of PTX treatment and/or β₂AR mutation on GIRK facilitation, expressed as a percentage of basal I_HK of the control (no PTX treatment, β₂AR^wt expressed). (Empty bars) Oocytes expressing β₂AR^wt; (hatched bars) oocytes expressing β₂AR^PF. (+ and −) Oocytes incubated or not treated with PTX. Calculated average values ± SEM from three different batches of oocytes (three oocytes/batch) are shown. (* and ***) Mean value deviates significantly ( P < 0.05 and 0.001) from the corresponding control group; i.e., oocytes without PTX treatment.