ABSTRACT
Dopamine is an endogenous neurotransmitter that has an active and diverse physiological role in both the central and peripheral nervous systems. It mediates its effects via dopamine receptors, historically defined as D1-like and D2-like (1). With the advent of molecular cloning techniques it has been determined that the dopamine receptor family consists of five distinct genes belonging to the superfamily of heptahelical receptors spanning the lipid bilayer and exert their biological effects via diverse intracellular signaling cascades. Two functional genes compose the mammalian D1-like receptor subfamily termed D1 and D5, and three genes-D2, D3, and D4-belong to the D2-like subfamily [reviewed (2)].
