Transcriptional profiling reveals that chronic social defeat stress produces a long-lasting and selective decrease in Rac1 mRNA expression in the NAc of susceptible, but not resilient, mice. (a) mRNA expression of small RhoGTPase-related genes in the NAc of C57BL/6J mice 48 hrs following their last social defeat exposure. (b) Temporal profile of Rac1 mRNA expression in the NAc 4, 24 and 48 hrs following chronic social defeat stress. (c) Correlation of 48 hr Rac1 mRNA expression with social avoidance behavior. (d) Rac1 mRNA expression following a 35 d schedule of once daily antidepressant administration (20 mg kg−1 imipramine or vehicle, i.p). (e) Total Rac1 protein levels 48 hr after chronic social defeat stress in the NAc. (f) Correlation of total Rac1 protein with social avoidance behavior. (g) Left bars represent NAc Rac1 mRNA expression 48 hr following a single acute social defeat stress. Right bars indicate NAc Rac1 mRNA expression 48 hr following an acute injection of imipramine (20 mg kg−1, i.p.) or vehicle in previously susceptible mice. All data presented as mean ± SEM, group size is indicated in either figure legends or within graph bars; (g) *P <0.05 compared by students t-test, (a, b, e) *P <0.05 by one-way ANOVA, (d) *P <0.05 by two-way ANOVA, (c,f) P <0.05 compared by Pearson's r.