In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

Though it's not glutamate, DARPP-32 is expressed in medium spiny neurons with this molecule's receptors and is phosphorylated by those receptors, thus becoming an inhibitor of protein phosphotase 1. Bupropion blocks reuptake of this and another molecule by binding to this molecule's transporter. That transporter is important in all four of this molecule's major pathways, which include the mesolimbic and the mesocortical. Tuberoinfundibular neurons secrete this neurotransmitter to inhibit Prolactin, which counteracts one of its effects. It is a precursor to other catecholamines like epinephrine and is mainly produced in the substantia nigra. One theory of schizophrenia is that it is related to hyperactive receptors of this compound. For 10 points, name this neurotransmitter which is used to treat Parkinson's disease.
Science