one of the other postings relates to this--though definitive answers are not available, someone is looking at this question....

relationship between clinical improvement and in vivo synaptic dopamine (DA) release

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Neurology. 2006 Nov 14;67(9):1612-7. Related Articles, Links


Clinical correlates of levodopa-induced dopamine release in Parkinson disease: a PET study.

Pavese N, Evans AH, Tai YF, Hotton G, Brooks DJ, Lees AJ, Piccini P.

MRC Clinical Sciences Centre and Division of Neurosciences, Faculty of Medicine, Imperial College, Hammersmith Hospital, Du Cane Road, London W12 ONN, UK.
CONCLUSION: In advanced Parkinson disease, the improvement of rigidity and bradykinesia and the presence of dyskinesias after a single dose of oral levodopa are governed by the level of dopamine generated at striatal D2 receptors. In contrast, relief of parkinsonian tremor and axial symptoms is not related to striatal synaptic dopamine levels and presumably occurs via extrastriatal mechanisms.