PSMA2 and attention deficit-hyperactivity disorder: SHRs (ADHD model) who received either MDL (5-HT2A antagonist) or IPS (5-HT1A agonist) or GFC (alpha-2 adrenergic agonist) showed a highly significant (p < 0.001) decrease in these study parameters (mean distance traveled, mean movement velocity) when compared to the SHR-NC group (Figure 1A,B).