The neurotrophins ("neuro" means nerve and "trophe" means nutrient) are a family of soluble, basic 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 able to support survival of sympathetic and sensory spinal neurons in culture. It is synthesized and secreted by sympathetic and sensory target organs and provides trophic support to neurons as they reach their final target.3 Neurotrophin secretion also increases in the nervous system following injury. Schwann cells, fibroblasts, and activated mast cells normally synthesize NGF constitutively, however direct trauma and induced cytokines combine to increase neurotrophin production in these cells after injury
