We have recently reported results of the optogenetic-microdialysis technique in knock-in mice expressing the long intracellular domain of D4.7, the product of a polymorphic variant of the D4R gene (DRD4) associated with attention deficit hyperactivity disorder (ADHD) and substance use disorders (SUD) (Bonaventura et al., 2017). The gene discussed is DRD4; the disease is attention deficit-hyperactivity disorder.