@article {Roussakise4, author = {Andreas-Antonios Roussakis and Marios Politis and David Towey and Paola Piccini}, title = {SEROTONIN-TO-DOPAMINE TRANSPORTER RATIOS IN THE STRIATUM OF PATIENTS WITH PARKINSON{\textquoteright}S DISEASE: IMPACT ON LEVODOPA{\textendash}INDUCED DYSKINESIAS}, volume = {86}, number = {11}, pages = {e4--e4}, year = {2015}, doi = {10.1136/jnnp-2015-312379.185}, publisher = {BMJ Publishing Group Ltd}, abstract = {Background Serotonergic mechanisms play a key role in the development of the Levodopa-induced dyskinesias (LIDs) in patients with Parkinson{\textquoteright}s disease (PD). We hypothesised that an unfavourable serotonin-to-dopamine terminal ratio in the putamen would be most detrimental in dyskinetic patients. We investigated the role of serotonin-to-dopamine transporter binding ratios in the development of dyskinesias in Parkinson{\textquoteright}s disease patients.Methods/Subjects Twenty-eight Parkinson{\textquoteright}s disease patients[17 with LIDs;11 stable] and 12 age and gender-matched healthy controls were studied with [11C]DASB PET and [123I]FP-CIT SPECT, Imaging. We have employed a simplified reference tissue model using cerebellar reference for the quantification of [11C]DASB, whereas a semi-quantification approach was used for [123I]FP-CIT. We estimated uptake values in the putamen.Results Parkinson{\textquoteright}s disease patients showed decreases in [123I]FP-CIT binding (p\<0.001) compared to controls, 51\% in the stable and 62\% in the LIDs group. PD patients showed decreases in [11C]DASB binding (p\<0.01), but there were no differences between the stable (37\% loss) and LIDs(31\% loss) groups. PD patients with LIDs had 103\% increased [11C]DASB-to-[123I]FP-CIT binding ratio, whereas in the PD stable group the ratio was increased by 76\%, relative to HCs. Higher [11C]DASB-to-[123I]FP-CIT binding ratio correlated with longer disease duration for the 28 PD patients (r=0.52;p\<0.01).Conclusion SERT-to-DAT ratio increases as PD progresses and patients experience LIDs.}, issn = {0022-3050}, URL = {https://jnnp.bmj.com/content/86/11/e4.96}, eprint = {https://jnnp.bmj.com/content/86/11/e4.96.full.pdf}, journal = {Journal of Neurology, Neurosurgery \& Psychiatry} }