GIRK channels in hippocampal pyramidal neurons are also activated by adenosine and serotonin10, 40, 41. To test whether GIRK2 isoforms promote preferential associations between GIRK channels and specific GPCRs, we measured GIRK currents evoked via these signaling pathways in Girk2 −/− pyramidal neurons expressing GIRK2a or GIRK2c. Both adenosine (Fig. 5F) and the 5HT1A receptor-selective agonist 8-OH-DPAT (Fig. 5H) evoked reliable currents in wild-type neurons, but not Girk2 −/− pyramidal neurons expressing EGFP. Girk2 −/− pyramidal neurons expressing either GIRK2a or GIRK2c exhibited adenosine- and 8-OH-DPAT-induced currents, and these currents were comparable in magnitude to those observed in wild-type control neurons (Fig. 5G,I). To gauge the influence of GIRK3 on the coupling between the GIRK2 isoforms and specific GPCRs, baclofen-, adenosine-, and 8-OH-DPAT-induced currents were also measured in infected Girk2 −/− /Girk3 −/− pyramidal neurons. While no differences were found in Girk2 −/− /Girk3 −/− pyramidal neurons expressing GIRK2a or GIRK2c, the currents measured in these neurons were larger than those recorded in Girk2 −/− pyramidal neurons expressing these isoforms (Supplementary Fig. S5).
