Basic research on the nerve growth factor (NGF) has led to the stimulating hypothesis that an important link in the neuronal aging process may be the reduced synthesis, availability and utilization of trophic factors. The hypothesis needs confirmation together with the understanding of the role and properties of the numerous factors which have joined NGF. Development, survival and death of the nerve cells seem to depend on the activity of an unexpectedly large number of trophic factors. However, their interactions and regional distribution, the distribution and specificity of their receptors, need to be investigated. Since some growth factors have already been used in man, such as the hemopoietic growth factors in blood diseases, and epidermal growth factor in intestinal atrophy, it is very likely that long before all basic information is marshalled, trophic factors will be administered to aged patients affected by Alzheimer's and other degenerative diseases. Let us hope that the results will not be disappointing and that a new therapeutic avenue might really have been opened.
