The effect of dopamine agonist therapy on dopamine transporter imaging in Parkinson's disease

Abstract

Single‐photon emission computed tomography (SPECT) imaging with the dopamine transporter ligand, [123I] β‐CIT (2β‐carboxymethoxy‐3β‐[4‐iodophenyl] tropane), has been proposed as a means of measuring Parkinson's disease (PD) progression. To be useful in this role, however, [123I] β‐CIT imaging should not be influenced by the medications used to treat PD, including the dopamine agonist drugs such as pergolide. We assessed the effect of adjunctive pergolide administration on [123I] β‐CIT uptake in 12 patients with PD, who were being treated with levodopa, initiating pergolide therapy for motor fluctuations. Patients underwent [123I] β‐CIT imaging at baseline, subsequently while on pergolide therapy (6 weeks), and again 4 weeks after pergolide wash‐out. Uptake in the striatum was averaged for the two sides and expressed as (striatum − occipital)/occipital, with similar calculations for putamen and caudate. Consistent with PD, the patients' mean striatal and putamen uptake ratios at baseline were significantly less (p <0.001) than the mean values from 26 normal control subjects of similar age. During pergolide treatment, the striatal and putamen [123I] β‐CIT uptake ratios were each statistically similar to baseline, although there was a slight trend toward an increased striatal value (8% higher on pergolide; p = 0.105). Caudate [123I] β‐CIT uptake was 11% higher on pergolide therapy (nominal p = 0.042, but not significant when adjusted for multiple comparisons: p = 0.126). After pergolide wash‐out, the striatal, putamen, and caudate uptake ratios did not differ from baseline. Therefore, we found that pergolide therapy did not significantly affect [123I] β‐CIT SPECT imaging but we cannot exclude a small influence.

[ 123 I]FP-CIT SPECT is a useful method to monitor the rate of dopaminergic degeneration in early-stage Parkinson's disease

“…Likewise, D 2 receptor agonists were indicated not to have any influence on binding of radioligands to the dopamine transporter (Dresel et al, 1988;Vander Borght et al, 1995;Little et al, 1996;Ahlskog et al, 1999 …”

Correlation of Parkinson's disease severity and duration with123I-FP-CIT SPECT striatal uptake

“…Animal studies have shown that acute administration of levodopa did not interfere with dopamine transporter imaging. 33 Innis et al 34 reported no significant effect of levodopa or selegiline on striatal dopamine transporters using 123 I-␤-CIT SPECT, and recently Ahlskog et al 35 found that pergolide did not significantly affect 123 I-␤-CIT uptake.…”

Assessing dopaminergic function in Parkinson?s disease: levodopa kinetic-dynamic modeling and SPECT

“…The use of low [ 123 I]-FP-CIT dose and the high pass reconstruction Wiener filter, affecting the semi-quantitative measurements of ROIs counts [25], may also be responsible for the relatively poor correlation of our SPECT results with the clinical characteristics of Parkinson's disease. Moreover, all patients were examined on their chronic antiparkinsonian therapy, and although controlled clinical studies have not found significant changes in striatal DAT after treatment with levodopa/carbidopa [19] or pergolide [1], potential direct or indirect effects of therapy on DAT regulation cannot be completely ruled out [14].…”