Figure 3.

Whole cell K⁺ currents from WT and α_i-null ES cell-derived cardiocytes are illustrated. (A) With WT cells a marked increase from basal (a) current was seen after perfusion of the recording chamber with (b) 10 μM carbachol. (B) Addition of the m2 muscarinic receptor antagonist (b) methoctramine (50 nM) did not affect basal current (a) but blocked the subsequent stimulation by carbachol (c). With α_i2-null cells (C) and α_i3-null cells (D) basal currents (a) were similar to WT cells but did not substantially increase after addition of carbachol (b).