SNCA and Parkinson disease: Given the importance of α-synuclein alterations in PD, some studies have focused on the effect of melatonin in α-synuclein expression and aggregation. In vitro studies showed that melatonin protects dopaminergic cells such as SK-N-SH from the neurotoxicity induced by amphetamine (AMPH) and prevents the toxic overexpression of α-synuclein that occurs when these cells are exposed to AMPH [110, 200].