CaMKIICre(+):Girk2 fl/fl mice (7–8 wk) were placed in a stereotaxic device (David Kopf Instruments; Tujunga, CA) under isoflurane anesthesia. Microinjectors were created by affixing a 33-gauge stainless steel hypodermic tube within a shorter 26-gauge stainless steel hypodermic tube, and were attached to polyethylene-20 tubing affixed to 10 μL Hamilton syringes. Microinjectors were lowered bilaterally through burr holes in the skull to the dorsal CA1 (bregma: −2.20 mm AP, ±1.60 mm ML, −1.40 mm DV) and 400 nL of AAV8-hSyn-DIO-GIRK2a-IRES-EGFP, AAV8-hSyn-DIO-GIRK2c-IRES-EGFP, or AAV8-hSyn-DIO-mCherry control virus (~1.3 × 1013 viral particles/mL) was injected per side over 4 min using a Pump 11 Elite infusion pump (Harvard Apparatus; Holliston, MA). The syringe was left in place for 10 min following infusion to reduce solution backflow along the infusion track. Behavioral experiments were performed 2 wk after surgery to allow for full recovery and viral expression. The accuracy of viral targeting was assessed in all experiments using fluorescence confocal microscopy. Images were acquired with MetaMorph Advanced Acquisition v. 7.7.7.0 software. GIRK-dependent signaling in CA1 pyramidal neurons expressing GIRK2a or GIRK2c, indicated by EGFP expression, was assessed by measuring baclofen-induced somato-dendritic currents in acutely isolated slices, as described6.
