Fig. 1.

Homooligomeric GIRK4 channels are regulated by PKA.

A.: Original current recording derived from an oocyte injected with cRNA encoding GIRK4 and m₂R. Membrane potential was kept constant at − 80 mV. Basal current (I_HK) was induced by changing from the physiological extracellular medium (ND96) to a medium containing 96 mmole/L K⁺ (HK). G-protein activation was achieved by perfusion with HK containing 10^− 5 mole/L acetylcholine. An injection needle was inserted during agonist activation. In order to activate PKA 3 pmole cAMP were injected into the cytosol of the oocyte (both insertion and injection are indicated by an arrow). After washout of agonist and HK, both I_HK and I_ACh were elicited again in order to demonstrate the increase of currents through GIRK4 complexes.

B.: Statistical analysis of the effect of injection of SpCAMPS, RpCAMPS and water on agonist induced currents through homooligomeric GIRK4^S143T complexes. Number of individual oocytes tested in parenthesis above each bar. **: the mean value deviates statistically significant from both RpCAMPS and H₂O at the p < 0.01 level.

C.: Statistical analysis of the effect of cAMP injection on basal currents and agonist induced currents through homooligomeric and heterooligomeric GIRK channel complexes. Number of individual oocytes tested in parenthesis above each bar. *, (***): the mean value deviates statistically significant from zero at the p < 0.05 (0.001) level.