BDNF and major depressive disorder: Peculiarly, the expression of D3 receptors has been demonstrated to be regulated by Brain-Derived Neurotrophic Factor (BDNF) in the nucleus accumbens during development and adulthood [31], a feature that tightly links these receptors to the developmental pathogenetic hypothesis of psychosis and depression, as well as the selective expression of D3 receptors in proliferative zones of striatal granule cells during embryonic development [32].