The genetic studies have identified associations between the SNPs in genes that are related to GPCRs and schizophrenia [135]; in particular, some metabotropic glutamate receptors (mGlu), subtype 3 (mGlu3), 5-hydroxytryptamine 2A receptor (5-HTA2A), and dopamine D3 receptors (DRD3). This evidence concerns the gene DRD3 and schizophrenia.