To further determine the role of 5-HT1A auto-receptors in this process, we used 5-HT1A receptor-knockout (KO) mice (Figure 5B, 2-way ANOVA, n = 6/group, 5A: F (1,20) = 5.298, p = 0.0322; 5B: F (1,20) = 43.13, p < 0.0001) with CFA-induced comorbid pain and depression. Here, HTR1A is linked to major depressive disorder.