During early life, BDNF influence almost all aspects of development in the CNS. BDNF function in early life include neuronal proliferation, neuronal migration, neuronal survival, neuronal protection, neuritogenesis, morphogenetic, and chemotropic effects, axon guidance, axonal branching, dendritic growth, dendrite branching, synapse formation and efficacy, neuronal excitability and synaptic transmission, short- and long-term plasticity, modulation of excitatory and inhibitory synapses, modulation and maturation of NMDA receptors, stimulation of neurotransmitter or neuropeptide synthesis, neurotransmitter release, etc. During development, BDNF function is major involved in survival, outgrowth, and differentiation of neurons.
In addition, BDNF function is associated in learning and memory. It has been suggested that decreased production of BDNF is a pathogenetic factor common to Alzheimer's disease and major depression, which might explain the association between the two disorders. Hippocampal samples from Alzheimer's disease donors show decreased BDNF expression, and individuals with Alzheimer's disease have low plasma levels of BDNF. Even more, major depression patients have lower levels of serum BDNF than normal control subjects. Parkinson's disease (PD) is characterized by the selective and progressive loss of dopaminergic neurons of the substance nigra. Individuals with PD present reduced BDNF expression in the substantia nigra, speciWcally in the pars compacta, as determined by immunocytochemistry . A reduction in BDNF protein was also detected in the caudate nucleus and putamen of PD patients, as quantified by a radio-enzymatic method. BDNF is also involved in eating behavior and physical activity.