GAD1 and schizophrenia: In addition to lower release probability, the strength of PVI-mediated inhibition is also thought to be lower in schizophrenia based on prior studies reporting lower levels of the GABA synthesizing enzyme GAD67 in PVIs10,40,41 and lower levels of GABAA1 receptor α1 subunit (GABAA1α1) mRNA in pyramidal neurons42,43.