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). D5 receptor has a 10-fold higher affinity for dopamine than the D1 receptor.