Fig. 1: In vivo whole-cell recordings of identified ventral mesencephalon dopamine neurons.

a. Schematic representation of the experimental setup. b. Representative recording of spontaneous in vivo electrical activity from a whole-cell-recorded and neurochemically-identified dopamine neuron in the ventral tegmental area (VTA) of an adult C57Bl/6 J mouse under isoflurane anesthesia. The upper trace displays action potentials with overshoot during a stable recording for > 5 minutes. The higher temporal resolution of the electrical activity in the lower trace allows visual identification of subthreshold events such as large hyperpolarizations and synaptic events. c. Immunocytochemical identification demonstrates the recorded neuron (top panel, filled with Biotin; red) is positive for tyrosine hydroxylase (TH; green). Lower magnification of the immunocytochemical image (lower panel) locates the recorded neuron (arrow) within the ventral region of the VTA (n = 112, N = 80). d. Depiction shows the location of the recorded neuron (large red dot) in relation to all the recorded neurons in this study (gray dots) displayed at three coronal planes. Bottom right panel is a 3D representation of the example cell location (red sphere) in relation to all recorded cells (gray spheres). e, f Plot of the mean firing rate (e) and coefficient of variation (CV) for interspike intervals (ISI, f) for each neuron presented in this study. Cyan and Yellow diamonds in panel F highlight the representative cells depicted in Fig. 2a–c and d–f, respectively. g Plot of the input resistance for each neuron where resistance was measured. h Log-scale plot of the instantaneous firing rate, and its full range, for each neuron presented in this study sorted in the order of increasing median rate. d–h The large red symbol in all plots represents the example neuron illustrated in b and c. Horizontal lines in e–g represent median.