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