Parkinson's Disease drug target

Parkinson's disease is associated with the degeneration of dopaminergic neurons.
There are neurotrophic factors (molecules that induce neuronal growth) associated with the formation of dopaminergic neurons in the mid-brain.
It is called Glial Derived Neurotrophic Factor(GDNF).
Since, Parkinson drugs target the dopamine pathway; the have side-effect of inducing psychosis. another drug target could be increasing cAMP, or stimulating the MAPK pathway in those cells.

However, it is important to note that the research done on GDNF occurred in developing neurons and not targeted at regeneration.