Fig. 6.

Activation of VP projections to VTA recapitulates behavioral responses. a Whole-cell recordings in the VTA reveal that single-pulse (5-ms, blue dash) photostimulation of VGAT⁺ VP terminals triggered PTx-sensitive IPSCs. Pie chart show the fraction of responding neurons, bar graphs show peak IPSC amplitude, insets shows individual cells pre- and post- PTx (n = 7, paired t-test, t₍₆₎ = 3.2, p = 0.019); and representative trace; numbers inside bars represent sample size. b Cell-attached recordings in the VTA show that photostimulation of GABA terminals from the VP consistently reduced action potential firing frequency in the VTA (n = 14, Wilcoxon matched-pairs signed-rank test, p = 0.0001). The black scatter plot shows mean change in firing rate 5-s before, during, and after 40-Hz photostimulation, gray axis and plots show individual neuron responses, inset (right) shows a representative trace. c VGAT-Cre mice displayed a preference for the compartment paired with photostimulation of VP terminals in the VTA on the RTPP assay (n = 11) and showed ICSS over three daily sessions (n = 4 YFP, n = 8 ChR2). d Whole-cell recordings, as described in a, show that photostimulation of VGLUT2⁺ VP terminals in the VTA triggered DNQX-sensitive EPSCs (n = 5, paired t-test, t₍₄₎ = 3.75, p = 0.019); e and cell-attached recordings, as described in b, show that train of photostimulation increased action potential firing frequency in the VTA (n = 14, Wilcoxon matched-pairs signed-rank test, p = 0.0001). f VGLUT2-Cre mice showed avoidance for the compartment paired with photostimulation of VP terminals in the VTA on the RTPP assay (n = 6). Example images of ChR2:YFP and optic fiber (OF) tracks in the VTA of c VGAT-Cre or f VGLUT-Cre mice; DAPI (blue), scale = 200 µm. Scales for a and d are 50 pA, 50 ms and 200 pA, 50 ms, respectively; scale for b and e is 1 s; *p < 0.05, **p < 0.01, ***p < 0.001. See also Supplementary Figure 7 and Supplementary Table 3