Striatal Cholinergic Interneuron Electrophysiology

Electrophysiological recording in the striatal ChIs was conducted as described previously (Zhao et al., 2016 (link)). Briefly, the pipettes had a resistance of 3–5 MΩ when filled with the internal solution consisted of (in mM): 80 CsOH, 80 gluconate acid, 30 CsCl, 40 HEPES, 10 tetraethylammonium chloride (TEA-Cl), 5 EGTA, 12 Na₂phosphoceatine, 1 MgCl₂, 2 Mg-ATP, 0.5 Na-GTP (265–270 mOsm/l), which was adjusted with CsOH to pH 7.3 (Miki et al., 2013 (link)). Slices were bathed in an external solution of (in mM): 105 NaCl, 20 TEA-Cl, 2 CaCl₂, 6 MgCl₂, 6 KCl, 26 NaHCO₃, 10 glucose, 3 myo-inositol, 2 sodium pyruvate, 0.5 ascorbic acid, 1.25 NaH₂PO4, 0.0005 tetrodotoxin (TTX, pH = 7.2 with TEA-OH, Miki et al., 2013 (link)). The slice in the recording chamber was visualized with a 40 × water-immersion objective (NIR Apo, Nikon, Japan) using standard infrared and differential interference contrast (IR-DIC) microscopy and a CCD camera. Cells in the striatum approximately 50 μm beneath the slice surface were patched. Electrophysiology was performed using an Axon 200B amplifier (Molecular devices, Foster city, CA, United States) and Clampex 10.1 software (Molecular devices) at room temperature 23 ∼ 25°C (Hawkins et al., 2015 (link)). Data were filtered at 2 kHz and digitized at 10 kHz online. Only those recordings with stable holding currents and access resistance were accepted.