HTR1A and depressive disorder: HTR1A was one of GPCRs and is one of the most widely expressed and abundant subtypes of serotonin receptors.[13] HTR1A, binding with its ligand 5‐HT (also known as serotonin), resulted in conformational changes and signaling pathway activation, such as PI3K/Akt and MAPK/ERK pathways.[20, 21] Studies regarding the function of HTR1A are mainly focused on the nervous system, such as regulating depression by regulating self‐tolerance by deregulating gene expression.