Basal firing of dopamine (DA) neurons in the ventral tegmental area (VTA) was recorded from horizontal midbrain slices prepared 7–10 days after a single injection of LPS. The experimenter was not blind to the treatment history. Mice were killed by cervical dislocation under halothane anesthesia, and horizontal midbrain slices (210 μm) containing the VTA were prepared. Slices were cut using a vibratome (VT1000S; Leica Microsystems, Bannockburn, IL) in ice-cold cutting solution containing (in mM): 205 sucrose, 2.5 KCl, 1.25 NaH2PO4, 7.5 MgCl2, 0.5 CaCl2, 10 glucose, 25 NaHCO3, saturated with 95% O2 and 5% CO2, and then incubated at 35 °C for >1 h in physiological saline containing (in mM): 126 NaCl, 2.5 KCl, 1.2 NaH2PO4, 1.2 MgCl2, 2.4 CaCl2, 11 glucose, 21.4 NaHCO3, saturated with 95% O2 and 5% CO2 (pH 7.4, ~295 mOsm/kg). Recordings were made at 34–35 °C in the same physiological saline perfused at 2–3 ml/min. Neurons were visualized using a 40x objective on an upright microscope (BX51WI; Olympus America, Center Valley, PA) with infrared/oblique illumination optics. Loose-patch recordings (~10–20 M Ω seal) of dopamine neuron
