BDNF and substance abuse: For example, in the adult brain, BDNF shows high levels of expression and regulates both excitatory and inhibitory synaptic transmission [8], and deficiency of BDNF signaling determines its role in the pathogenesis of a number of brain diseases and mental disorders, such as Huntington’s disease, Alzheimer’s disease, ischemic stroke [9,10], stress-related disorders [11,12], substance abuse [13,14], eating disorders, mood disorders [15,16,17], and schizophrenia [18,19].