a protein (see growth factor), consisting of two polypeptide chains, that is required for the development and longevity of some neurones, including those in the sympathetic nervous system and some central nervous system and sensory neurones. Nerve growth factor is necessary for axon growth and also for initiating new neuronal connections with other cells. The role of NGFs in preventing the degeneration of brain cells is being explored in research into Alzheimer's disease.
Medical dictionary. 2011.