BDNF

Brain-derived neurotrophic factor (BDNF) is a 27 kDa secreted homodimeric protein and the most abundantly expressed neurotrophin in the adult mammalian brain. It binds the high-affinity tyrosine-kinase receptor TrkB and the low-affinity p75 neurotrophin receptor (p75NTR) to drive neuronal survival, axonal and dendritic growth, synaptic plasticity (notably long-term potentiation in the hippocampus), and adult neurogenesis in the subgranular and subventricular zones. BDNF is synthesised as a precursor (proBDNF) that is proteolytically processed to mature BDNF; the relative balance of pro- and mature forms regulates whether the predominant signal is pro-survival (via TrkB) or pro-apoptotic (via p75NTR). Reduced BDNF expression and serum concentration have been documented in major depressive disorder, Alzheimer's disease, Parkinson's disease, and following traumatic brain injury, generating substantial pharmacological interest in BDNF-pathway upregulation. In peptide research, BDNF is a primary readout for the cognitive-nootropic class — semax (an ACTH 4-10 analogue) and selank (a tuftsin analogue) are reported to upregulate hippocampal BDNF expression in rodent models, providing a mechanistic basis for their reported procognitive effects. BDNF is also relevant to exercise and recovery research as the principal mediator of exercise-induced cognitive and mood benefit.