Skf38393

Ghrelin (rat, mouse) was purchased from Phoenix Pharmaceuticals (Burlingame, CA). Tetrodotoxin (TTX), bicuculline (Bic), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and d-2-amino-5-phosphonopentanoic acid (AP5), quinpirole, SKF38393 and sulpiride were from Tocris Bioscience (Ellisville, MO). Dopamine was from Sigma-Aldrich (St. Louis, MO). Drugs were prepared and stored as stock solutions according to the manufacturer’s instructions and diluted in ACSF to obtain the experimental concentrations used in each experiment. All drug solutions were administered by a large-diameter (300 μm) flow pipe with the tip directed toward the recorded cell. During periods of no drug application, normal ACSF was continuously supplied to the recorded cell through the flow pipe.

The extracellular recording solution used for dissection and for measuring light-evoked currents contained (in mM) 125 NaCl, 2.5 KCl, 1 MgCl2, 1.25 NaH2PO4, 2 CaCl2, 20 glucose, and 26 NaHCO3. For voltage clamp recordings, the intracellular solution contained (in mM) 120 CsOH, 120 gluconic acid, 1 MgCl2, 10 HEPES, 10 TEA-Cl, 10 phosphocreatine-Na2, 4 Mg-ATP, 0.5 Na-GTP, 10 EGTA and 50 μM Alexa Fluor 488 (Invitrogen, Carlsbad, California, USA) and was adjusted to pH 7.2 with CsOH. Extracellular solutions were bubbled with 95% O2–5% CO2. To isolate the inhibitory receptor inputs, SR-95531 (SR, 20 μM) to block GABA_A receptors, (1,2,5,6-tetrahydropyridine-4yl) methyphosphinic acid (TPMPA, 50 μM) to block GABA_C receptors, and strychnine (1 μM,) to block glycine receptors were used (Mazade & Eggers, 2013 (link), 2016 (link)). To test dopamine D1 receptors, the D1 receptor agonist SKF-38393 (SKF, 20 μM, Tocris) was used with a concentration similar to previous studies (Ichinose & Lukasiewicz, 2007 (link); Liu et al., 2016 (link); Mazade et al., 2019b (link)). All drug solutions were applied to the slice for five minutes before recordings began using a gravity-driven superfusion system (Cell Microcontrols, Norfolk, VA), with continuous perfusion throughout the experiment (~1–2 mL/minute). Unless otherwise indicated, all chemicals were obtained from Sigma-Aldrich (St. Louis, MO, USA).

During two consecutive days before any procedure (habituation phase) mice were injected in their home-cage with NaCl 0.9% (i.p.). On the test day, animals were perfused for 6 hours with NaCl 0.9% or TG and received injections (i.p.) of d-Amphetamine sulfate (3 mg/kg, A5880, Sigma-Aldrich, L’Isle d’Abeau, France), haloperidol hydrochloride (0.5 mg/kg, #0931, Tocris Biosciences, Bristol, United Kingdom), raclopride (0.6 mg/kg, #1810, Tocris Biosciences, Bristol, United Kingdom) or SKF38393 (10 mg/kg, #0922, Tocris Biosciences, Bristol, United Kingdom). All drugs were dissolved in NaCl 0.9%.