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PATH51 Investigating adenosine A2A receptor availability in Parkinson's disease patients with and without levodopa induced dyskinesias with [11C]SCH442416 PET

Objective To investigate adenosine 2A (A2A) receptor availability in Parkinson's disease (PD) patients with and without levodopa induced dyskinesias (LID). Background Levodopa use is key to treatment in PD. Its use is associated with the development of LID. Adenosine regulates dopamine release so dyskinesias may be related to changes in striatal A2A availability. We have studied A2A receptor availability in PD patients with and without LID using [11C]SCH442416 PET, a marker of A2A receptor function. Design/methods Six PD patients with LID and six without LID were studied withdrawn from medications. Results were compared with three age matched controls. Using spectral analysis, [11C]SCH442416 regional volumes of distribution were computed. Striatal and thalamic binding potentials (BP) reflecting the ratio of specific:nonspecific uptake were compared between groups. Results Striatal A2A binding of PD subjects with LID was significantly raised (p=0.017). This was also reflected in striatal subdivisions. Thalamic BP was similar between all PD subjects. The striatal BPs of controls lay within the BP range of the PD subjects without LID. Conclusion PD patients with LID show increased striatal A2A receptor availability. This provides a rationale for using A2A receptor antagonists in the management of dyskinesias.