Interesting interview with Jack Clark, neurologist out of University of Toronto, who seems to get that we need to move beyond dopamine replacement therapy. He even calls it "Parkinson's Diseases" we have different etiologies with same clinical features.

Highlight of what he has to say at The Dana Organization; there is also a fantastic visual that can be printed for reference.

...Parkinson’s disease is far more than a degeneration of the nigrostriatal dopamine system. Instead, it is a widespread process involving multiple brain systems, including those involving noradrenaline, serotonin, acetylcholine, and other neurotransmitters.

Moreover, as the disease progresses, patients develop a number of symptoms that respond poorly if at all to dopamine replacement therapy. These symptoms—now commonly believed to occur due to involvement of non-dopaminergic brain regions—account for a very large proportion of the disability seen in the later stages of the disease.

Just as man needed to move beyond the Ptolemaic belief that the earth was the center of the universe around which the sun and planets revolved, I feel that we now need to go beyond the belief that dopamine is the center of the Parkinson Universe