Neurotrophins are a family of regulatory proteins that are necessary for the growth, survival, and differentiation of neurons in the central and peripheral nervous systems [82]. In addition, they modulate neuronal transmission, synapto-genesis, and play a role in modulating the plasticity of neurons [82-84]. The neurotrophin family includes brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurexins (NRXN) 3-7, which are involved in the development of neural networks as well as higher level processes such as learning, memory, and behavior [85]. The role of neurotophins in substance dependence disorders can be speculated to be a result of deregulated synaptic plasticity or differential binding affinities of these neurotrophins to their associated receptors [85].
