Serotonin content and uptake in platelets can distinguish Parkinson's disease from control patients and essential tremor.

We have demonstrated that platelets from Parkinson's disease patients exhibit impaired serotonin uptake and release. This seems to be caused by a dysfunction in secretory vesicles (SecVs), which share the mechanisms of accumulation with dopaminergic neurons. As a working hypothesis, this dysfunction may create an excess of dopamine causing neurotoxicity a process absent in other conditions like Essential Tremor or Essential Tremor Plus. The serotonin functional analysis in platelets is a potential tool to reduce misdiagnosis.To validate this, we performed a functional study using liquid chromatography (UHPLC) to analyze serotonin content, uptake, and secretion in platelets from 50 Parkinson's disease patients, 23 essential tremor, 17 essential tremor plus, and 50 controls.Parkinson's disease patients show impaired platelet serotonin content and uptake vs. Controls (P < 0.001), essential tremor (P < 0.01) and essential tremor plus (P < 0.05), ANOVA. Notably, no significant differences were found between controls and essential tremor nor essential tremor plus; although, essential tremor plus manifested mild serotonin storage dysfunction.Platelet serotonin dysfunction reflects distinct pathological origins between Parkinson's disease and other tremor syndromes, suggesting that platelet serotonin analysis is a viable and objective tool for differential diagnosis between Parkinson's disease and tremor syndromes.