Neuronotrophic and neurite-promoting factors and their clinical potentials

Neuronal maintenance and neuritic growth during development are increasingly recognized as being under the extrinsic control of neuronotrophic- and neurite-promoting agents. Protein agents ('factors') are the most studied but not the only molecules exerting such controls. It appears increasingly likely that adult neurons in situ are equally subject to similar extrinsic regulations. Two recently studied in vivo models for peripheral and central neural regeneration have demonstrated trauma-related accumulations of neuronotrophic- and neurite-promoting factors in the adult rat, in close temporal correlation with neuronal maintenance and axonal regrowth, respectively. Deficits in the supply or utilization of similar factors may underlie neuronal or glial regressive processes in aging, and in selected neuronal diseases such as Parkinson, ALS and Alzheimer. Speculative approaches to, and potential problems of, clinical interventions addressing putative neuronotrophic deficits are discussed.