The neurotrophins (“neuro” means nerve and “trophe” means nutrient) are a family of soluble, basic protein growth factors which regulate neuronal development, maintenance, survival and death in the CNS and the PNS. NGF, the first member of the family to be discovered, was originally purified as a factor supporting and regulating survival, development, function and plasticity of sympathetic and sensory spinal neurons in central and peripheral nervous systems in vivo as well as in vitro. It is synthesized and secreted by sympathetic and sensory target organs and provides trophic support to neurons as they reach their final target. Neurotrophin secretion increases in the nervous system following injury. Schwann cells, fibroblasts, and activated mast cells normally synthesize NGF constitutively, however, direct trauma and induction of cytokines combine to increase neurotrophin production in these cells after injury.