Trophic factors.

The various neurotrophic factors influence a wide range of cell functions in the developing, mature and injured nervous system. Recent studies have provided valuable insights on the receptors that mediate these effects and on the intracellular events that follow the binding of the ligand. Although growth factors were known to be expressed by non-neuronal cells in the targets and pathways of neuronal projections, it is now clear that the neurons themselves can also be a source of these molecules. A better understanding of the mechanisms of action of trophic factors on the survival and differentiation of neurons, coupled with advances in methods for the delivery of these molecules to the nervous system have provided an impetus for exploring their use as aids to the protection and regeneration of the injured nervous system.