The D₁ dopamine receptor (D₁ receptor, DRD1) is one of five receptors that mediate the effects of the catecholamine neurotransmitter dopamine. Dopamine regulates a variety of functions including locomotor activity, emotion, positive reinforcement, food intake, and hormone secretion. The dopaminergic system has been extensively studied in the last thirty years mainly because its dysregulation has been linked to several neurological and neuropsychiatric diseases including Parkinson’s disease and Schizophrenia¹.

All five dopamine receptors belong to the 7-transmembrane domain, G-protein coupled receptor (GPCR) superfamily.

Historically, the five receptors have been divided into two subfamilies based on pharmacological and structural considerations: the D₁-like subfamily (that includes the D₁ and D₅ subtypes) and the D₂-like subfamily (that includes the D₂-, D₃- and D₄ subtypes)¹.

The D₁-like receptors are coupled to G_s-type G proteins and enhance adenylate cyclase activity while the D₂-like receptors are coupled to G_i-type G proteins and inhibit adenylate cyclase activity¹.

The D₁ receptor is widely distributed throughout the brain with the highest expression in the cerebral cortex and striatum. In the periphery the D₁ receptor has been detected in the adrenal cortex, kidney and heart.

Functionally, the D₁ receptor has been implicated in the regulation of both locomotor and cognitive functions including the maintaining of spontaneous motor behaviors, the control of working memory and cognition as well as the regulation of craving and reward pathways.

In addition, the D₁ receptor plays an important role in the pathogenesis of hypertension by regulating epithelial Na⁺ transport and by interacting with vasoactive hormones/humoral factors, such as aldosterone and angiotensin^1,2.