Brain Slice Preparation and Electrophysiology

Adult male and female rats were anesthetized with isoflurane and killed (Bara et al., 2018 (link); Borsoi et al., 2019 (link)). The brain was sliced (300 μm) in the coronal plane with a vibratome (Integraslice, Campden Instruments) in a sucrose-based solution at 4°C (87 mm NaCl, 75 mm sucrose, 25 mm glucose, 2.5 mm KCl, 4 mm MgCl₂, 0.5 mm CaCl₂, 23 mm NaHCO₃, and 1.25 mm NaH₂PO₄). Immediately after cutting, slices containing the medial PFC or the NAc were stored for 1 h at 32°C in a low-calcium artificial CSF (ACSF) that contained the following: 130 mm NaCl, 11 mm glucose, 2.5 mm KCl, 2.4 mm MgCl₂, 1.2 mm CaCl₂, 23 mm NaHCO₃, and 1.2 mm NaH₂PO₄, and were equilibrated with 95% O₂/5% CO₂ and then at room temperature until the time of recording. During the recording, slices were placed in the recording chamber and superfused at 2 ml/min with low Ca²⁺ or normal Ca²⁺ ACSF (PFC and NAc, respectively). All experiments were done at 32°C (PFC) or 25°C (NAc). The superfusion medium contained picrotoxin (100 mm) to block GABA-A receptors. All drugs were added at the final concentration to the superfusion medium.