GAD1 and Parkinson disease: Although the downregulation of two key markers of GABAergic cells (glutamic acid decarboxylase-67 (GAD67) and calcium-binding protein parvalbumin (PV)) was evidenced in the dorsolateral prefrontal cortex of PD patients, without cell loss, the role of GABAergic neurotransmission in premotor stages of PD has not been established yet, which needs to be elucidated in future studies [1].