Glial cell line-derived neurotrophic factor (GDNF) has been identified as a potent neurotrophic factor that enhances survival of midbrain dopaminergic neurons. GDNF is a glycosylated, disulfide-bonded homodimer. It promotes the survival and morphological differentiation of dopaminergic neurons and increases their high-affinity dopamine uptake. On the basis of these findings, it has been sμggested that GDNF may play a role in the treatment of Parkinson’s disease, which is marked by progressive degeneration of midbrain dopaminergic neurons.