NEUROTROPHINS AND NERVE INJURY IN THE ADULT

A role for neurotrophins in mature primary sensory neurons persists, e xtending beyond that of promoting survival during development, to one of maintaining phenotypic and functional properties. Many adaptive cha nges that occur after peripheral axotomy and in axonal repair are beli eved to be influenced by altered availability of neurotrophic molecule s to the neuron in this state. Indeed, administration of exogenous ner ve growth factor counteracts many degenerative changes observed in the subpopulation of axotomized neurons which are nerve growth factor-res ponsive. Current efforts focus on defining actions of other neurotroph ins (brain-derived neurotrophic factor, neurotrophin-3 and neurotrophi n-4/5) in nerve injury and repair, and the intracellular pathways invo lved. Knowledge gained from work focusing on nerve growth factor and n eurotrophin-3 in supporting maintenance or modulation of aspects of th e differentiated state of adult primary sensory neurons is discussed.