More specifically, dopaminergic signaling pathways, such as mesolimbic, mesocortical, and nigrostriatal pathways, are affected in obesity with decreased excitability and down-regulated dopamine receptor and dopamine transporter (DAT) expression within the nucleus accumbens, ventral tegmental area (VTA), and the striatum as obesity progresses [219,220]. This evidence concerns the gene SLC6A3 and obesity due to melanocortin 4 receptor deficiency.