To test this hypothesis, the densities of interneurons expressing PV (GABAergic), cells endowed with D2, and fibers expressing TH were compared in the PFC and motor cortex (MC) of SHRs, considered to be a validated animal model of ADHD, and Wistar Kyoto rats (WKYs), which served as the control strain (40). The gene discussed is TH; the disease is attention deficit-hyperactivity disorder.