Acute Coronal Brain Slice Preparation

Acute coronal brain slices were prepared as previously described^{34 (link)}. Briefly, 7 days after surgery the animals were anesthetized with isoflurane (Forane®, AbbVie) and decapitated. Brains were rapidly removed and immersed in ice-cold oxygenated protective artificial cerebrospinal fluid (aCSF, 95% O₂, 5% CO₂) containing (in mM): N-methyl-D-glucamine 110, HCl 110, KCl 2.5, NaH₂PO₄ 1.2, NaHCO₃ 25, D-glucose 25, MgSO₄ 10, CaCl₂ 0.5, Na-ascorbate 1 and Na-pyruvate 2.9, osmolarity: ~310 mOsm/kg, pH adjusted to 7.4 with HCl^{35 (link)}. The brains were trimmed with a scalpel blade and glued onto the stage of a vibrating microtome (VT1200S, Leica Microsystems). Coronal slices (thickness 300 µm) containing both the prelimbic and the infralimbic subregions of the prefrontal cortex were cut in oxygenated ice-cold protective aCSF and subsequently incubated at 32–34 °C for 5 minutes. After this recovery period, the slices were transferred to standard oxygenated aCSF containing (in mM): NaCl 125, NaHCO₃ 25, D-glucose 25, KCl 2.5, NaH₂PO₄ 1.25, CaCl₂ 2 and MgCl₂ 1, osmolarity: ~310 mOsm/kg, pH adjusted to 7.4 with HCl^{36 (link)} at room temperature for at least 30 minutes before the electrophysiological recordings.