Objective: We aimed to investigate the central serotonergic function in de novo PD and change in serotonergic function with dopaminergic medications.

Background: While dopaminergic dysfunction has been the focus of attention in Parkinson’s disease (PD) for decades, serotonergic dysfunction in central nervous system may also play an important role in motor and non-motor symptoms in PD.

Method: A total of 30 patients with unmedicated PD were enrolled between September 2013 and January 2017. All subjects underwent comprehensive neurological examination, laboratory tests, brain magnetic resonance imaging, Unified Parkinson’s Disease Rating Scale (UPDRS), and loudness dependence of the auditory evoked potentials (LDAEP). The latencies and amplitudes of N1 and P2 peaks were measured at the Cz electrodes and LDAEP was calculated as the slope of the two peaks with five stimulus intensities. LDAEPs were performed twice, at baseline (pre-LDAEP) and at12 weeks (post-LDAEP) after dopaminergic medications.

Results: The mean age was 68.9 years (SD, 11.1), and the mean age at onset was 67.2 years (SD, 11.7). Male patients accounted for 66.7% (N=20). The modified Hoehn and Yahr stage was 2.2 (SD, 0.5) and mean score of UPDRS III was 31.9 (SD, 13.2). After 12 weeks, the mean dose of levodopa equivalent dose was 436.4 (SD, 175.4). There was only a trend but not statistically signification correlations between age at onset and pre-LDAEP (p=0.06). There were no significant differences in demographics, pre-LDAEP, and post-LDAEP between male and female patients.

Conclusion: This study suggests that serotonergic functions might be relatively preserved in earlier-onset of PD patients. The findings of this study may shed light on levodopa-induced dyskinesia or impulsivity in earlier-onset of PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/serotonergic-function-in-de-novo-parkinsons-disease/