Whole-cell patch-clamp recordings

Whole-cell patch-clamp recordings were made from pyramidal cells in the CA1 region³⁸. A recording patch pipette (3–6 MΩ) was filled with the internal solution containing (in mM): 122.5 K-gluconate, 17.5 KCl, 10.0 HEPES, 0.2 EGTA, 2.0 MgATP, 0.3 Na₃GTP and 8.0 NaCl (pH 7.2, 295–305 mOsm). The series resistance and the input resistance were monitored throughout the experiment, and if they changed by more than 20% or the series resistance was above 30 MΩ, the data were discarded. A bipolar tungsten stimulating electrode was placed in the same layer as in the field-potential recording. Cells were held at − 60 mV (the liquid-junction potential was not corrected) and AMPA receptor-mediated EPSCs were recorded, which were adjusted to be 200–300 pA in amplitude. When GABA_B receptor-dependent IPSCs were recorded, picrotoxin (100 µM) was added to the external solution. After recording stable EPSCs for 10 min, non-N-methyl-d-aspartate (NMDA)-receptor antagonist CNQX (10 µM) and the NMDA-receptor antagonist d-(−)-2-amino-5-phosphonopentanoic acid (50 µM) were added, and the GABA_B receptor-mediated IPSC was recorded for further 10 min. The amplitude of GABA_B receptor-mediated IPSCs was measured by averaging the value for 10 ms around the peak. In some experiments, we confirmed that the isolated IPSCs were blocked completely by {"type":"entrez-protein","attrs":{"text":"CGP55845","term_id":"875097176","term_text":"CGP55845"}}CGP55845 (not shown).