SLC6A3 and major depressive disorder: Neurodegeneration in brain regions involved in depression and apathy (Krashia et al., 2022), particularly that of dopaminergic neurons in the substantia nigra and ventral tegmental area (VTA), along with decreases in dopamine transporters in the cortex and hippocampus of 5xFAD mice, plays a significant role in apathy and depression-like symptoms (Vorobyov et al., 2019).