To evaluate the effect of GLP-1R on depression-like and anxiety-like behaviors in diabetic mice, age-matched wild-type (WT) mice and db/db mice were administered saline or the GLP-1R agonist EX-4 at a dose of 5 μg/kg, the chemical structure of which is shown in Figure 1A. The db/db mice exhibited high blood glucose and body weight; nevertheless, short-term administration of EX-4 only induced effects consistent with the hypoglycemic effect but had no influence on body weight (Figure 1C,D). This evidence concerns the gene GLP1R and major depressive disorder.