DRD2 and schizophrenia: In schizophrenia, the balance between D2R and RGS activities is considered to be biased toward D2R (Fig 6A), because D2R blockers works as antipsychotic drugs for schizophrenia [52,53], and schizophrenia shows show a supersensitivity of D2R and/or an increase in striatal DA [29,60] as well as a decrease in striatal RGS9–2 [31,32].