Studies involving NAcc medium spiny neurons were conducted at room temperature, and recording electrodes contained the K-gluconate pipette solution described above or an alternative solution lacking K+ (in mM): 117 cesium gluconate, 2.8 NaCl, 20 HEPES, 0.4 EGTA, 5 tetraethylammonium-Cl, 2 MgATP, and 0.3 MgGTP, pH 7.2–7.4. mEPSC amplitudes and frequencies measured in wild-type NAcc neurons did not differ for these two pipette solutions and as such, data were pooled. Medium spiny neurons were identified by their morphology and hyperpolarized resting membrane potential (−75 to −85 mV). mEPSCs were measured at Vhold = −80 mV in the presence of picrotoxin (100 μM) and either lidocaine hydrochloride (0.6-0.8 mM) or TTX (1 μM). mEPSC data were filtered at 2 kHz, digitized at 5-10 kHz, and collected and analyzed using custom software (Igor Pro; Wavemetrics, Lake Oswego, OR).
