Dopamine receptor responsible for neuronal signaling in the mesolimbic system of the brain; an area of the brain that regulates emotion and complex behavior. Activated by dopamine; but also by epinephrine and norepinephrine; and by numerous synthetic agonists and drugs. Agonist binding triggers signaling via G proteins that inhibit adenylyl cyclase. Modulates the circadian rhythm of contrast sensitivity by regulating the rhythmic expression of NPAS2 in the retinal ganglion cells.