Neurotrophin Protocols

Introduction Neurotrophins are a family of growth factor proteins sharing a considerable degree of primary sequence and tertiary structure homology (1–4). Members of this protein family, including nerve growth factor (NGF), brain-derived neu- rotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4/5 (NT-4/5), have been identified as important signals in the developing peripheral nervous system where they serve as survival-promoting and differentiation factors for various populations of neurons (5,6). The presence of each of these factors within the central nervous system (CNS) has also been confirmed (7–12), although their physiological role in the CNS has yet to be fully elucidated. Identifying where in the CNS these proteins are made, where they are stored, how they are transferred from one cell to another, what cells they are trans- ferred to, and their final fate are some key steps toward reaching an under- standing of endogenous neurotrophin function.