The Pathologic Roles and Therapeutic Implications of Ghrelin/GHSR System in Mental Disorders

Ghrelin is a hormone consisting of 28 amino acids. Growth hormone secretagogue receptor (GHSR) is a receptor for ghrelin, which is expressed in the brain, pituitary gland, and adrenal glands, especially in the hypothalamus. The binding of ghrelin to the receptor 1a subtype mediates most of the biological effects of ghrelin. Ghrelin has a close relationship with the onset of psychosis. Ghrelin can affect the onset of psychosis by regulating neurotransmitters such as dopamine, γ-aminobutyric acid (GABA), and 5-hydroxytryptamine (5-HT) through the hypothalamus–pituitary–adrenal (HPA) axis, brain–gut axis, the mesolimbic dopamine system, and other ways. Ghrelin activates neuropeptide Y (NPY) in the hypothalamic arcuate nucleus (ARC) through the GHSR. Ghrelin binds to neurons in the ventral tegmental area (VTA), where it promotes the activity of dopamine neurons in the nucleus accumbens (NAcs) in a GHSR–dependent way, increasing dopamine levels and the reward system. This article summarized the recent research progress of ghrelin in depression, anxiety, schizophrenia, anorexia nervosa (AN), and bulimia nervosa (BN), and emphasized its potential application for psychiatric disorders treatment.