Fig. 4.
Center–perimeter analysis reveals no difference between WT and α2A-AR-KO mice but an apparent anxiogenic effect of imipramine in both genotypes. WT (open symbols) and α2A-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 for 20 min sessions. The time spent in the perimeter (outer four infrared beam widths, 75% of the floor area of the chamber) is recorded for each of four 5 min blocks throughout the 20 min session (mean ± SEM, n = 8–16 mice per group). Genotype effect, F(1,64) = 0.321, p = 0.57. Drug effect,F(2,64) = 7.318, p= 0.0014. Time block effect, F(3,192) = 34.8, p < 0.0001. Bonferroni–Dunn post hoc test: imipramine versus no injection, mean difference = 40.23, critical difference = 15.8, p < 0.0001; imipramine versus saline, mean difference = 20.8, critical difference = 13.7, p = 0.0003.