FGF20 and Parkinson disease: Finally, it should be noted that fgf2 is also deficient in dopaminergic neurons in Parkinson disease (Tooyama et al. 1993) and fgf2 and fgf20 actually act in concert to protect dopaminergic neurons from oxidative injury and to promote their repair (Krieglstein et al. 1998; Ohmachi et al. 2000; Otto and Unsicker 1990; Shults et al. 2000), so that the combined deficit in both these neurotrophic factors, superimposed on organophosphate-induced oxidative stress, may render striatal dopamine pathways especially vulnerable.