CRH and major depressive disorder: The potential mechanisms of depression-like behavior effects include hypothalamic–pituitary–adrenal (HPA) axis activity, which results in elevated serum concentrations of corticotropin-releasing hormone (CRH), adrenocorticotrophic hormone (ACTH) and corticosterone (CORT), indicators of depression-like behaviors [20,21,22], and the expression of glucocorticoid receptors (GR) and 5HT2AR in the prefrontal cortex (PFC), amygdala and hippocampal CA1 areas [23,24].