Figure 6.

Photoinhibition of DRN GABA neurons prevented the acquisition but not the expression of social avoidance behavior. Two cohorts of GAD2-Cre mice were injected in the DRN with Cre-dependent AAV vectors, driving expression of Arch-GFP or a sham tdTomato protein selectively in DRN GABA neurons. The first cohort (A, top row: photoinhibition during training) received daily photoinhibition during 20 min of sensory contact after physical aggression. The second cohort (A, bottom row: photoinhibition during testing) received photoinhibition only during the social interaction task. Heat maps depict representative behavioral effects of DRN GABA photoinhibition. Corresponding group averages are shown for the time spent in the interaction zone in Control and Defeated mice receiving photoinhibition during the sensory contact period (B) or during the social interaction task (C). Light application during daily sensory contact period abrogated social avoidance in Arch-GFP-targeted but not in tdTomato-targeted mice (two-way ANOVA, Fisher's post hoc; defeated Arch/stim vs defeated Arch/no stim *p = 0.011; defeated Arch/stim vs defeated tdTomato ***p < 0.001; n = 6–8 per group). In contrast, no significant effects were observed when light was applied during the social interaction task (two-way ANOVA, Fisher's post hoc; Arch CTRL vs DEF ***p < 0.001). Note that GABA photoinhibition had no effect on the behaviors of mice tested in the absence of a social target and that laser illumination per se was devoid of effect in mice expressing tdTomato.