Dopamine agonists and Parkinson's disease progression: What can we learn from neuroimaging studies

Progressive Presynaptic Dopaminergic Deterioration in Huntington Disease

“…Our observations of a mean annual rate of change of j5.8% for caudate and j9.6% for putamen are consistent with the rate of presynaptic degeneration in PD, and postsynaptic degeneration in PD and HD. 8 To conclude, our findings suggest that [ 123 I]-FP-CIT SPECT imaging is useful in ascertaining the presence of presynaptic dopaminergic dysfunction in Huntington disease, 9,10 and measuring nigrostriatal dopaminergic deterioration over time. It may become a useful biomarker for the disease and provides an objective method for measuring the effectiveness of neuroprotective therapies.…”

Neuroimaging and therapeutics in movement disorders

“…FDOPA PET and ␤-CIT SPECT show a 4% to 13% yearly reduction in baseline putamen uptake compared with 0 -2.5% in healthy controls in longitudinal studies. 6,7 This technique has also been used to estimate the duration of the preclinical period of PD using a linear regression analysis. 16 Striatal FDOPA measurements correlate with dopamine cell counts measured in postmortem specimens 17,18 and striatal DAT binding decreases with age in healthy volunteers and PD patients.…”

“…3,4 Brain imaging in movement disorders was originally introduced to visualize the pathological changes associated with different clinical syndromes. 5 Subsequently, these techniques have been used in longitudinal studies designed to assess disease progression 6,7 and the effects of potential neuroprotective strategies. 8 -10 Lately, functional imaging has also been applied in the objective assessment of symptomatic treatment responses.…”

Molecular imaging: The latest generation of contrast agents and tissue characterization techniques

“…Several disease states, including depression, the antipsychotic drug induced negative syndrome of schizophrenia, Parkinson's disease, and extrapyramidal Parkinson‐plus neurodegenerative syndromes are characterized by focal or regional decreases in DAT and D2 receptor binding [Ilgin et al, 2001; Prunier et al, 2001; Winogrodzka et al, 2001; Wong, 2002]. Opiates and Parkinson's disease have both been shown to effect the DAT system with SPECT imaging using two novel radiopharmaceuticals; [ 123 I]β‐CIT, a cocaine analog with a binding constant of 1.6 nM for the DAT and [ 123 I]FP‐CIT, a tracer that has been successful at documenting the accelerated pre‐synaptic dopaminergic degeneration found in Parkinson's patients [Marek et al, 2003]. Diseases characterized by abnormal increases in D2 receptor binding potential include attention order‐deficit‐hyperactivity disorder (ADHD), mania, and schizophrenia.…”