The brain-derived neurotrophic factor (BDNF) is a protein molecule which belongs to the neurotrophin family of growth factors. It encourages the growth and differentiation of new neurons and synapses, helping to support the survival of existing neurons. Although the brain-derived neurotrophic factor is present in high concentration in hippocampus and cerebral cortex, it is also found in other parts of the central nervous system, retina, kidneys, and prostate. Secreted from dense-core vesicles, the BDNF is made in the endoplasmic reticulum and binds at least two receptors on the surface of cells that are capable of responding to this growth factor, Track B and low-affinity nerve growth factor receptor (LNGFR), which is also known as p75.
Brain-derived neurotrophic factor takes part in axonal growth, pathfinding and in the modulation of dendritic growth and morphology. Major regulator of synaptic transmission and plasticity at adult synapses in many regions of the CNS. The versatility of BDNF is emphasized by its contribution to a range of adaptive neuronal responses including long-term potentiation (LTP), long-term depression (LTD), certain forms of short-term synaptic plasticity, as well as homeostatic regulation of intrinsic neuronal excitability. It has been reported that chronic antidepressant treatment leads to an up-regulation of brain-derived neurotrophic factor (BDNF) mRNA levels in the hippocampus, and that physical activity (voluntary running) enhances this effect.