Slow inhibitory postsynaptic currents (slow IPSCs) in dorsal CA1 pyramidal neurons were evoked by electrical stimulation within proximal (Schaeffer collateral/SC) or distal (perforant path/PP) dendritic fields. SC and PP slow IPSCs were reliably observed in wild-type CA1 pyramidal neurons (Fig. 6C), and were blocked completely by the GABABR receptor antagonist CGP54626 (2 μM, not shown). Slow IPSCs were not observed in Girk2 −/− CA1 neurons expressing EGFP. While viral expression of either GIRK2a or GIRK2c in Girk2 −/− slices restored both SC and PP slow IPSCs in CA1 pyramidal neurons, the relative amplitudes of slow IPSCs measured in SC and PP differed between the groups (Fig. 6C). Indeed, the ratio of slow IPSC amplitudes, measured in PP and SC for each neuron, was significantly smaller in Girk2 −/− CA1 pyramidal neurons expressing GIRK2a, as compared to both wild-type control neurons, and Girk2 −/− pyramidal neurons expressing GIRK2c (Fig. 6D).
