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

Figures

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  Figure 1.. The serotonin management tests can differentiate Parkinson's disease (pd) from tremor syndromes. Platelets were isolated using our optimized protocol for measuring serotonin (5-HT). Specific (net) serotonin uptake was calculated after subtracting the non-specific component obtained by incubating platelets with the same serotonin concentrations in the presence of 1 µM reserpine (30 min prior and during serotonin incubation). Pooled data are shown as means ± 95% confidence interval from 50 Parkinson's disease patients (PD, red dots), 23 essential tremor (ET, dark blue dots), 17 essential tremor plus (ET+, light blue dots) and 50 controls (Ctrl, black dots), representing the average of duplicate measurements normalized to total protein. *p < 0.05; **p < 0.01; ***p < 0.001 (ANOVA). Standard deviation was used for statistical purposes and for establish the threshold of “pathological values”. No significant differences were found neither between control and essential tremor nor essential tremor plus (p = 0.52). See data points in Figure 2 of SM.

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  Figure 2.. Secretory features of platelets. A, After centrifugation of the platelet suspension, serotonin (5-HT) was analyzed in the pellet (platelet content) and in the supernatant (Sup) both from quiescent platelets (Basal) and after triggering release with 4 U/mL of thrombin for 90 s. B, The fractional release [ = serotonin in supernatant/(serotonin released + serotonin in supernatant)] showed a significant increase in the serotonin leakage only on Parkinson's disease (PD) platelets under basal conditions. Conversely, evoked release of platelets from Parkinson's disease was significantly lower than controls and essential tremor (ET). *p < 0.05; **p < 0.01; ***p < 0.001 (unpaired Students’ t test). The other comparisons resulted in non-significant differences. n = 39 Control (Ctrl), 40 Parkinson's disease, 21 essential tremor, and 15 essential tremor plus (ET+).