Extended Data Fig. 7: DA concentration profiles for various optogenetic stimulation protocols of DA fibres.
From: Dopamine D2 receptors in discrimination learning and spine enlargement
a, Schematic of virus injection (left) and amperometric detection of ChR2-driven DA release (right). A carbon fibre electrode was placed in the lateral NAc. b, c, Confocal images showing the expression of ChR2-mCherry in DA neurons in the VTA (b) and NAc (c). Scale bars indicate 500 μm for top parts and 5 μm for bottom parts of b, c. d, e, Replication of tonic DA levels in the NAc slice. Blue light pulses (2 ms) were applied at 5 Hz for 160 s with constant intensity (d, bottom) or modulated intensity (e, bottom). Amperometry signals for the evoked DA are shown (d, e, top). At the onset of stimulation, a strong but transient DA release which reflected long-term absence of autoinhibition was observed, whose peaks are omitted in the display. Insets show comparisons of averaged DA concentration between the first 10 s (1–11 s) and the last 10 s (150–160 s). Two-sided Wilcoxon signed-rank test for constant (n = 8 slices, W = 0, *P = 0.017) and for modulation (n = 9 slices, W = 14, P = 0.31). f, Time course averaged every 10 s over the stimulation period of 160 s. g, Plots of averaged tonic DA concentration. Each dot represents the averaged DA concentration indicated in the grey bar in f for each slice. h, Trace of DA concentration (top) and DA stimulation commands (bottom). During 5-Hz blue light stimulation, a 2-s pause was inserted 15 times in every 10 s. i, Averaged trace of the DA dip over 15 dips. To allow quick recovery to tonic levels, 5 pulses at 10 Hz were added after the pause. j, Plots of DA levels with various DA dips. Baselines indicate the average of 1 s before the dip onset and troughs indicate the average during the last 0.1 s of each dip. n = 14 (dip 2 s), 8 (dip 0.6 s) and 12 slices (dip 0.4 s). k, Plots of DA changes by various DA dips. Baseline values were subtracted from trough values. Two-sided Wilcoxon signed-rank test (dip 2 s, n = 14 slices, W = 0, **P = 4.0 × 10−4; dip 0.6 s, n = 8 slices, W = 0, **P = 0.003; dip 0.4 s, n = 12 slices, W = 0, **P = 7.0 × 10−4). l, Trace of DA concentration (top) and DA stimulation commands (bottom). During 5-Hz blue light stimulation, 20-Hz stimulation (dark blue) with an enhanced stimulation intensity was inserted 15 times every 10 s. m, Averaged trace of DA concentration over 15 bursts. n, Plots of DA levels by various DA bursts. Baselines indicate the average of 1 s before the burst onset and troughs indicate the average during the last 0.1 s of each burst. n = 11 (burst 1 s) and 7 slices (burst 0.5 s). o, Plots of DA changes by various DA bursts. Baseline values were subtracted from peak values. Two-sided Wilcoxon signed-rank test (burst 1 s, n = 11 slices, W = 0, **P = 0.003; burst 0.5 s, n = 7 slices, W = 0, **P = 0.003). Error bars and shading indicate s.e.m. Samples of slices are biological replicates.
