Dopamine is the predominant catecholamine neurotransmitter found in mammalian brain, where it controls a variety of functions including locomotor activity, cognition, emotion, positive reinforcement, food intake, and endocrine regulation. It also plays multiple roles in the periphery as a modulator of cardiovascular function, catecholamine release, hormone secretion, vascular tone, renal function, and gastrointestinal motility. The dopamine receptor family consists of five members, which are classified into two groups, D1-like (D1 and D5) and D2-like (D2, D3, and D4). Dopamine receptor 2 is mainly expressed in the brain. It has splicing variants, D2L and D2S. D2R receptor is implicated in a number of neurological and psychiatric conditions. Drugs acting at dopamine D2 receptors (D2R) are commonly used to alleviate symptoms for Parkinson's disease, schizophrenia, and depression.