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Volume 11 (2011), Pages 1726-1734
Review Article

Serotonergic Dysfunction in Parkinson's Disease and Its Relevance to Disability

Centre for Neuroscience, Division of Experimental Medicine, Hammersmith Hospital, Imperial College London, London W12 0NN, UK

Received 6 June 2011; Accepted 24 August 2011

Academic Editor: R. E. Tanzi

Copyright © 2011 Marios Politis and Clare Loane. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Growing evidence suggests that Parkinson's disease is not solely affecting the dopaminergic system. Results from biochemical, animal, postmortem, and functional imaging studies have revealed that other neurotransmitter systems are affected as well, including the serotonergic system. With the use of in vivo positron emission tomography functional imaging, it has been shown that serotonergic terminals are affected at a varying, nonlinear degree starting early in the clinical course of Parkinson's disease. Tremor and the majority of nonmotor symptoms do not seem to respond adequately to dopaminergic medication. Recent studies suggest that serotonergic dysfunction has a direct relevance to Parkinson's disease symptoms, the so-called nonmotor symptoms, including depression, fatigue, weight changes, and visual hallucinations. These in vivo findings indicate that agents acting on the serotonergic system could help towards alleviating these symptoms. This paper aims to review the current literature and to highlight the need for further in vivo investigations.