Neurons were visualized on an Olympus scope (BX51WI) equipped with fluorescence and whole-cell patch-clamp recordings were made from neurons in the posterior medial VTA, defined as the region medial to the medial terminal nucleus of the accessory optical tract. DA neurons were identified by presence of Ih current, large capacitance (30–50 pF) and slow spontaneous firing (1–3 Hz) (Cruz et al., 2004; Labouèbe et al., 2007; Lammel et al., 2008; Padgett et al., 2012). Pitx3-GFP mice expressing GFP in DA neurons (Zhao et al., 2004) and viral expression of GFP/YFP in DAT-Cre+/− cells were used to confirm electrophysiological identification of DA neurons.
