a, Experimental groups. b, Schematic of illumination pattern; 473-nm light used to elicit phasic bursts of activity in ChR2-expressing VTA dopamine neurons. c, Phasic illumination of VTA dopamine neurons rescues stress-induced reduction in struggling on TST in ChR2 CMS but not eYFP CMS mice (**P < 0.001; eYFP CMS = 26.8 s ± 3.5 s; ChR2 CMS = 28.0 s ± 2.7 s; ChR2 non-CMS = 55.63 s ± 4.4 s; eYFP non-CMS = 56.0 s ± 4.7 s). Two-way ANOVA revealed a significant group-by-light epoch interaction (F6,134 = 6.04, P < 0.0001) and a significant influence of experimental condition on performance as revealed by one-way ANOVA (F3,67 = 6.20, P = 0.0009; Bonferroni post-hoc test). Error bars, s.e.m. d, Illumination parameters, as used in the TST, did not change locomotor activity in the open field, with no significant group-by-epoch interaction in two-way ANOVA (F9,152 = 0.99, P = 0.4493), and no detectable differences revealed by Bonferroni post-hoc tests on the same timescale. Error bars, s.e.m. e, Phasic activation of VTA dopamine neurons rescued the stress-induced decrease in sucrose preference in ChR2 CMS, but not eYFP CMS mice; one-way ANOVA, Dunn’s post-hoc test comparing baseline to light-on epoch, P < 0.01 for ChR2 CMS mice, P = 0.2851 for eYFP CMS mice. Two-way ANOVA revealed a significant group-by-light epoch interaction (F6,62 = 4.33, P = 0.001), and a significant influence of experimental condition on performance was revealed by one-way ANOVA (F3,31 = 3.40, P = 0.0299); **P < 0.01 for ChR2 CMS mice. Error bars, s.e.m.