Page "Dopamine" Paragraph 43

Dopamine binds to and activates a group of receptors called the dopamine receptors to mediate its physiological effects in the body.

The dopamine receptors are a series of five G protein-coupled receptors ( GPCRs ), which consist of the D < sub > 1 </ sub >, D < sub > 2 </ sub >, D < sub > 3 </ sub >, D < sub > 4 </ sub >, and D < sub > 5 </ sub > receptors.

As GPCRs, they work by modulating the cyclic adenosine monophosphate ( cAMP ) second messenger system to produce a cellular response.

The five receptors are individually categorized into two distinctive groups based on their varying properties and effects, the D1-like and D2-like subfamilies.

The D < sub > 1 </ sub > and D < sub > 5 </ sub > receptors belong to the D1-like subfamily.

They are coupled to G < sub > s </ sub > and increase the cellular concentrations of cAMP by the activation of the enzyme adenylate cyclase.

The D < sub > 2 </ sub >, D < sub > 3 </ sub >, and D < sub > 4 </ sub > receptors belong to the D2-like subfamily.

They are coupled to G < sub > i </ sub >/ G < sub > o </ sub > and decrease the cellular concentrations of cAMP by inhibition of adenylate cyclase.

Ultimately, the cAMP second messenger system, through several downstream mechanisms, works by modulating the opening of plasmalemmal ion channels that allow positively charged ions such as Na < sup >+</ sup > and K < sup >+</ sup > to enter or exit the cytoplasm of the cell, thereby generating or inhibiting an action potential.

The receptors also couple directly to ion channels via the G-proteins.

The D1-like receptors have various effects on neuronal activity, while the D2-like receptors tend to decrease action potential generation and are therefore usually inhibitory.