Hippocampal slice preparation for electrophysiology

Briefly, mice were anesthetized with isoflurane and decapitated following University of California, Los Angeles, Chancellor's Animal Research Committee protocol. Horizontal 350-μm slices were cut on a Leica VT1000S vibratome in ice-cold N-methyl-d-glutamine (NMDG)-based HEPES-buffered solution, containing the following: 135 mm NMDG, 10 mm d-glucose, 4 mm MgCl₂, 0.5 mm CaCl₂, 1 mm KCl, 1.2 mm KH₂PO₄, 20 mm HEPES, and 27 mm sucrose (bubbled with 100% O₂, pH 7.4, 290–300 mOsm/l). Then, slices were incubated at 32°C in a reduced sodium artificial CSF (ACSF), containing the following: 85 mm NaCl, 25 mm d-glucose, 55 mm sucrose, 2.5 mm KCl, 1.25 mm NaH₂PO₄, 0.5 mm CaCl₂, 4 mm MgCl₂, and 26 mm NaHCO₃, pH 7.3–7.4 when bubbled with 95% O₂, 5% CO₂. After 30 min, low sodium ACSF was substituted for normal ACSF at room temperature, containing the following: 126 mm NaCl, 10 mm d-glucose, 2 mm MgCl₂, 2 mm CaCl₂, 2.5 mm KCl, 1.25 mm NaH₂PO₄, 1.5 mm Na pyruvate, 1 mm l-glutamine, and 26 mm NaHCO₃, pH 7.3–7.4 when bubbled with 95% O₂, 5% CO₂. For recording, brain slices were transferred to a submerged recording chamber at 34°C and perfused at 5 ml/min with ACSF. All salts were purchased from Sigma-Aldrich.