BNDF is the second member of the neurotrophin family trophic factors, isolated first from the pig brain. BDNF is a polypeptide consisting of 119 amino acid residues, and forms a homodimer. BDNF is expressed in the brain and also in peripheral tissues. There are two types of receptors binding to BDNF: tropomyosin receptor kinase B (TrkB), the high-affinity receptor, and p75NTR, the low-affinity receptor. TrkB has a tyrosine-kinase domain in its cytoplasmic region. There are two truncated isoforms of TrkB that have no tyrosine-kinase domain. BDNF regulates the growth, maintenance, and survival of certain target neurons as. Well as synaptic plasticity, learning, and memory through the activation of TrkB. On the other hand, the role of p75NTR is less clear.