Fig. 5.

Light–dark analysis reveals an apparent anxiogenic effect of the knock-out of the α_2A-AR after injection stress and an anxiogenic effect of imipramine. WT (open symbols) and α_2A-AR-KO (filled symbols) mice were subjected to injection with saline (A, circles), imipramine (B, squares), or no injection (C, triangles) and placed in the open field chambers with the light–dark insert included (see Materials and Methods) for 20 min sessions. The time spent in the dark half of the chamber is recorded for each of four 5 min blocks throughout the 20 min session (mean ± SEM, n = 8–14 mice per group). Repeated measures ANOVA results, all groups: genotype effect,F_(1,56) = 0.774, p= 0.383; drug effect, F_(2,56) = 2.77,p = 0.072; time block effect,F_(3,168) = 40.24, p< 0.0001; time block × genotype interaction,F_(3,168) = 2.91, p= 0.0363. Saline plus imipramine groups only, repeated measures ANOVA results: genotype effect, F_(1,35) = 2.15, p = 0.152; drug effect,F_(1,35) = 5.46,p = 0.025; time block effect,F_(3,105) = 26.3, p< 0.0001; time block × genotype interaction,F_(3,105) = 4.66, p= 0.0042.