GABBR2 and schizophrenia: Some associations are extraordinary relevant to the major hypothesis of the onset and etiology of schizophrenia, including serotonin and dopamine as significantly altered compounds (Table 2), and associated gene polymorphisms (GRM8, PTGS1, GABBR2), covering glutamatergic, serotonergic, GABAergic, and dopaminergic synapse transmission and.