SLC6A3 and attention deficit-hyperactivity disorder: In previous studies DAT KO rats showed locomotor hyperactivity, cognitive dysfunctions and deficits in sensorimotor gating, as well as traits of compulsive behavior (Cinque et al., 2018; Leo et al., 2018b)–endophenotypes found in psychiatric disorders associated with altered dopaminergic signaling like attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), bipolar disorder and schizophrenia (Leo et al., 2018a).