(A) Example of a recorded transduced DA neuron labeled with neurobiotin (blue) and identified with TH (red) and GFP (green) labeling. 3 out of 7 recorded neurons have been filled with neurobiotin, of which all were confirmed as DAergic by TH labeling. (B) Left, average change in firing rate for VTA DA neurons (n = 7) upon nicotine injection in darkness, and under 390 (purple) and 520 nm light (green). Right, average change in burst firing frequency upon nicotine injection in darkness, and under 390 (purple) and 520 nm light (green); only the busting VTA DA neurons were considered here (n = 3). (C) Average changes in firing rate (top) and in the percent of spikes within bursts (SWB, bottom) for VTA DA neurons from control (left, light grey, n = 37) and β2E61C-transduced animals (right, dark grey, n = 7), upon nicotine i.v. injection (30 μg/kg) in darkness. (D) Changes in firing frequency are not different between control (Δfiring rate = 39.4 %, n = 37) and β2E61C-transduced animals (Δfiring rate = 31.7 %, n = 7, p=0.53). Similarly, changes in the percent of SWB are not different between control and β2E61C-transduced animals (Δ%SWB = 6.44 % and 10.72%, respectively, p=0.68). All values represent mean ± SEM.