BDNF and psychiatric disorder: Several psychostimulant adaptive molecules in the NAc are known to be involved in psychiatric disorders, including the cAMP response element-binding protein (CREB) [8, 9], brain-derived neurotrophic factor (BDNF) [10, 11], orexin [12], and Shati/Nat8l [5, 13]; however, key signaling pathways and novel molecular cascades related to behavioral regulation still remain to be identified.