Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family of growth factors which includes nerve growth factor (NGF), neurotrophin-3 (NT-3) and neurotrophin-4/5 (NT-4/5).

All neurotrophins are synthesized as preproneurotrophin precursors that are subsequently processed within the intracellular transport pathway to yield proneurotrophins that are further processed to generate the mature form. The mature form of BDNF is a non-covalent stable homodimer that can be secreted in both constitutive and regulated pathways.

BDNF conveys its activity by binding to two classes of receptors, a member of the Trk receptor tyrosine kinase family (TrkB) and the pan-neurotrophin receptor p75^NTR. Binding of BDNF to the TrkB receptor triggers ligand-induced dimerization and autophosphorylation of tyrosine residues. This activates various signaling cascades such the MAPK, PI3K and PLCγ pathways that are involved in cell growth, survival and differentiation of neurons in the central and peripheral nervous system.

Interestingly, recent evidence suggests that BDNF may influence target cell function via ion channel modulation. Ion channel activity in the target cells can be modulated by a TrkB-mediated mechanism that has not yet been determined. BDNF is able to block both K_V1.3 and AMPA-subtype glutamate ion channel currents in sensory neurons, while it can induce activation of the TRPC3 cation channel in neurons and of the Na_V1.9 Na⁺ channel in hippocampal neurons. These newly recognized BDNF actions underlie its “rapid” neuronal functions that include changes in neuronal excitability, plasticity and synaptic transmission.