Brain-derived neurotrophic factor (BDNF) along with nerve growth factor (NGF), neurotrophin-3 (NT-3), and neurotrophin-4/5 (NT-4/5) are members of the neurotrophin family of trophic factors. The neurotrophins play essential roles in the development, survival, and function of a wide range of neurons in both the peripheral and central nervous systems. The neurotrophins interact with two cell surface receptors, the low affinity P75 receptor and the Trk family of high affinity tyrosine kinase receptors. NGF preferentially binds TrkA, BDNF and NT4/5 bind TrkB, and NT-3 binds TrkC (and TrkA to a lesser extent).