Since dysregulation of the hypothalamic-pituitary adrenal (HPA) axis can lead to the onset of anxiety-like behavior and depression, we compared in Gpr3−/− and wild-type mice the levels of serum corticosterone, the major glucocorticoid end product in rodents, both under basal conditions and in response to the stress induced by the tail suspension test. Here, GPR3 is linked to major depressive disorder.