Fig. 1.

G-protein-dependent and independent K⁺ current activation in oocytes injected with cRNA for GIRK1, 2, and 3 as well as combinations of GIRK1, GIRK2, or GIRK3 with GIRK5 or antisense for GIRK5. Currents were recorded using a two-microelectrode voltage clamp from oocytes injected with cRNA for the m2 muscarinic receptor, GIRK1, 2, 3, and 5, and GIRK5 antisense oligonucleotide KHA1, as described in Materials and Methods. Currents were recorded from a holding potential of −80 mV in response to step voltages between −150 and 50 mV in 20 mV increments, the interval between steps was 1 sec. The basal current was determined in a solution in which all the Na⁺ was isosmotically replaced with K⁺; G-protein current activation was determined in response to 5 μm carbachol added to the extracellular solution. Bars represent a summary of current data at −150 mV for all subunit combinations recorded 72 hr after injection for both basal K⁺ and total current (basal plus carbachol-induced in high K⁺ solutions). Bars represent mean ± SEM measure at −150 mV.