Third, systemic administration of D1R agonists strongly stimulates motor activity in rodent and non-human primate PD models and PD patients (Mailman et al., 2001; Li and Zhou, 2013); equally important, microinjection of a D1 agonist into the dorsal striatum but not GPe, SNr or the motor cortex induces strong motor activity in parkinsonian animals (Wang and Zhou, 2017). Here, DRD1 is linked to Parkinson disease.