Enhanced recovery of the nigrostriatal dopaminergic system in MPTP-treated mice following intrastriatal injection of basic fibroblast growth factor in relation to aging.

Studies have suggested that the restorative effects of adrenal medullary chromaffin cell grafts in animal models of Parkinson's disease may be related to trophic factors contained within the chromaffin cells. Basic fibroblast growth factor (bFGF) is present in chromaffin cells and has been shown to exert trophic effects on dopaminergic neurons in vitro. Basic FGF was stereotaxically injected into the striatum of young (2-month-old) and aging (12-month-old) C57BL/6 mice which had been treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) 1 week earlier. MPTP treatment reduced tyrosine hydroxylase (TH)-immunoreactive (IR) fibers in the striatum and striatal dopamine (DA) concentration in both the young and older mice 5 weeks later. Computerized image analysis of striatal DA fibers in young mice treated with bFGF showed significant recovery of DA fibers up to 600 microns from the injection site 5 weeks after MPTP administration. Striatal DA fibers in older mice treated with bFGF showed significant recovery only up to 300 microns from the injection site, and the degree of recovery was very limited compared with young mice. HPLC analysis of DA concentration revealed that striatal DA in young mice recovered significantly when treated with bFGF, but no significant recovery was observed in older mice. It is concluded that bFGF enhances the recovery of striatal DA systems from MPTP toxicity both in young and in older mice, but that such benefits are very limited in older mice.