DRD4 and schizophrenia: The cluster of interactive proteins related to GPCR signaling included multiple proteins coded by genes previously linked to antipsychotic mechanisms of action [including DRD4 (22), HTR1 (23), NTSR1 (24), and ADRA2C (25)], reported in transcriptional studies of post mortem brain tissue [e.g., PTGER3, S1PR1, ITPR2, and EDNRB (15, 26)], or associated with risk SNPs for schizophrenia [e.g., DRD5, OPRM1, and CNR1 (27, –29)].