Slices were superfused with a bicarbonate-buffered aCSF maintained at 30°C–32°C as described previously (Rice and Cragg, 2004 and Threlfell et al., 2010). Extracellular DA concentration ([DA]o) was monitored using fast-scan cyclic voltammetry (FCV) with 7-μm-diameter carbon fiber microelectrodes (CFMs; tip length 50–100 μm) and a Millar voltammeter (Julian Millar, Barts and the London School of Medicine and Dentistry) as described previously (Threlfell et al., 2010). In brief, the scanning voltage was a triangular waveform (−0.7V to +1.3V range versus Ag/AgCl) at a scan rate of 800V/s and sampling frequency of 8 Hz. Electrodes this website were

calibrated in 1–2 μM DA in each experimental media. For further details, see Supplemental Experimental Procedures. For whole-cell patch-clamp studies (in isolation or in combination with FCV), 300 μm coronal slices containing CPu and NAc were prepared in ice-cold high-sucrose aCSF containing 85 mM NaCl, 25 mM NaHCO3, 2.5 mM KCl, 1.25 mM NaH2PO4, 0.5 mM CaCl2, 7 mM MgCl2, 10 mM glucose, and 75 mM sucrose after decapitation

under halothane anesthesia. Slices were then transferred to oxygenated aCSF (95% O2/5% CO2) containing 130 mM NaCl, 25 mM NaHCO3, 2.5 mM KCl, 1.25 mM NaH2PO4, 2 mM CaCl2, 2 mM MgCl2, and 10 mM glucose at 35°C for 30–45 min and then maintained at room temperature check details until recording. During recordings, slices were superfused

with aCSF saturated with 95% O2/5% CO2 at 32°C. Whole-cell patch-clamp electrodes (4–7 MΩ) were filled with an intracellular solution containing 120 mM K-gluconate, 10 mM KCl, 10 mM HEPES, 4 mM MgATP, 0.3 mM NaGTP, 10 mM Na-phosphocreatine, and 0.5% biocytin. ChIs in the striatum were identified by their distinctive morphological features (Figure S1A) (large somas and thick primary dendrites) and their Quisqualic acid characteristic electrophysiological properties, prominent Ih, AHP, and broad action potential (Figures S1B–S1D, Table S1). Intracellular recordings were obtained using a Multiclamp 700B amplifier and digitized at 10–20 kHz using Digidata 1440A acquisition board. While performing current-clamp recordings, a small amount of holding current (typically <−25 pA) was injected when necessary to keep the cell close to its initial resting membrane potential (−60mV). Biocytin was included in the intracellular solution to allow post hoc visualization and confirmation of cell identity. All data were analyzed offline with Clampfit (pClamp 10), Neuromatic (http://neuromatic.thinkrandom.com), and custom-written software running within IgorPro environment. ChR2-expressing fibers were activated using a 473 nm diode laser (DL-473, Rapp Optoelectronic) coupled to the microscope with a fiber optic cable (200 μm multimode, NA 0.