DRD2 and schizophrenia: A breakthrough developed in the DA D2R field and its link to schizophrenia when different types of D2R heteroreceptor complexes were discovered in the forebrain (Fuxe et al., 1998; Hillion et al., 2002; Liu et al., 2006; Borroto-Escuela et al., 2013c, 2014c, 2016a; Figure 5).