Fig. 5. Chemogenetic suppression of VTA VGluT2 neuron activity blocks nonassociative behavioral consequences of inescapable stress.
A Illustration of the experimental setup in which VGluT2 hM4Di or VGluT2 control (CTL) mice received yoked-inescapable shock (IS; 100 tail shocks, average intertrial interval 60 sec). Ten minutes prior to IS or home cage treatment, VGluT2 hM4Di, VGluT2 CTL, and no stress home cage controls (HC) received clozapine (0.1 mg/kg; i.p.). B Twenty-four hours following tailshock stress, mice were tested for sex-specific outcomes of IS. Males were tested for sociability and fear; females were tested for exploratory behavior in the light/dark box. n = 13 IS VGluT2 CTL, 8 IS VGluT2 hM4Di, 9 HC, 14 ES for males and 9 HC, 6 IS, 8 IS VGluT2 CTL, 9 IS VGluT2 hM4Di, 10 ES for females. C Quantification of interaction behavior with a social (same-sex conspecific) or a nonsocial (empty chamber) stimulus 24 h following stress treatment. HC, IS VGluT2 hM4Di, and ES mice spent significantly more time with the social stimulus compared to the nonsocial stimulus. IS VGluT2 CTL mice spent equal time with both social and nonsocial stimulus types. D Preference for the social stimulus compared to the nonsocial stimulus (social score) significantly differed between HC, ES, IS VGluT2 hM4Di, and IS VGluT2 CTL groups. IS VGluT2 hM4Di, HC, and ES groups did not differ from one another. E Mean time spent freezing in response to the delivery of two footshocks in a novel context. IS VGluT2 CTL mice showed enhanced freezing which was absent in IS VGluT2 hM4Di, unstressed HC mice, and ES mice. F–G In wild-type female mice, IS led to increased latency to exit the dark compartment compared to HC and ES female mice (F) and decreased time spent in the light compartment (G) of the light/dark box compared to HC female mice. H–I Following IS, VGluT2 CTL mice, but not VGluT2 hM4Di mice show increased latency to exit the dark compartment (H) and decreased time spent in the light compartment (I) of the light/dark box. Data are mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001; ANOVA with Sidak multiple comparison post hoc test.