Brain imaging will be conducted three times during this study. Study participants will travel to IND for \[123I\]ß-CIT and SPECT imaging (scan 1). Subjects will be randomized to no treatment, treatment with either levodopa, or treatment with Mirapex and undergo treatment for a period of 12 weeks. Subjects will return to IND for \[123I\]ß-CIT and SPECT imaging (scan 2) after 12 weeks of treatment and withdraw from the medication following the scan. Eight to 12 weeks after medication withdrawal, a final \[123I\]ß-CIT and SPECT imaging study (scan 3) will be performed at IND. The imaging outcome, striatal uptake of \[123I\]ß-CIT, from scan 1 (untreated) and scan 2 (treated with levodopa or pramipexole) will be compared to determine if there is a significant change in the uptake of the marker that may be attributed to levodopa or pramipexole treatment. In addition, scan 3 will be compared to scan 2 to determine the duration and reversibility of any regulatory effect that occurs. The subjects will be randomized, but not blinded to study drug assignment. The imaging technologist and all imaging analyses will be performed by investigators blinded to study drug assignment.
