| Summary: | Abstract Objective With a combination of different sympathetic tests, we aimed to elucidate whether impairment of sympathetic function in Parkinson's disease (PD) is the consequence of a central or peripheral efferent dysfunction. Methods Thirty‐five patients with early‐to‐intermediate PD (median age: 63 years; IQR: 57–67 years; disease duration 1–9 years, 15 women) and 20 age‐ and sex‐matched healthy controls (median age: 64.5 years; IQR: 58–68 years; 10 women) were recruited. Autonomic testing was performed in two subgroups and included the assessment of resting cardiovascular parameters, postprandial hypotension (PPH), orthostatic hypotension (OH), and vasoconstriction induced by intradermal microdialysis with different concentrations of norepinephrine (NE; 10–5; 10–6; 10–7; 10–8) and by cold through forehead cooling. We also used sympathetic multiunit microneurography (muscle sympathetic nerve activity; MSNA; burst frequency (BF): bursts per minute; burst incidence (BI): bursts per 100 heart beats) and evaluated the presence of phosphorylated α‐synuclein deposits in skin innervation in biopsies from the thighs by immunohistohemistry. Results Diastolic blood pressure was higher in the PD group at rest (p < .001) and during OH (F = 6.533; p = .022). Vasoconstriction induced by NE microdialysis and cold was unchanged in PD patients. MSNA was lower in PD patients than in controls (BF: p = .001; BI: p = .025). Phosphorylated α‐synuclein deposits could be found only in PD patients. Conclusion We did not find indications for peripheral sympathetic nerve fiber dysfunction or adrenoreceptor sensitivity changes. The decreased MSNA argues in favor of central sympathetic impairment.
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