DRD1 and Parkinson disease: The robust and sustained activity of orally-administered PF-2334 in both non-human primate eye blink response and the unilateral 6-OHDA lesioned rodent model of parkinsonism is consistent with the reduced β-arrestin recruitment and desensitization in vitro, and highlights the potential for compounds from this new class of non-catechol D1R selective ligands to address shortcomings with prior selective D1R ligands.