Retention of basic fibroblast growth factor immunoreactivity in dopaminergic neurons of the substantia nigra during normal aging in humans contrasts with loss in Parkinson's disease.

A count of pigmented neurons per mm3 in sections of the substantia nigra at the level where the oculomotor nerve emerges in 11 neurologically normal controls aged 15-82 showed the expected slow loss of such neurons with age. Most (82 +/- 3.8%) of the pigmented neurons showed immunoreactivity for basic fibroblast growth factor (bFGF) and this percentage was unaffected by age. This is in marked contrast to the case in Parkinson's disease where only some 12.7 +/- 2.6% of the remaining dopaminergic neurons showed bFGF-like immunoreactivity, providing further evidence against the hypothesis that Parkinson's disease is due to some early insult followed by age-related attrition of the remaining neurons.