Sympathetic vasoconstrictor reflexes in Parkinson's disease with autonomic dysfunction.

Centrally and locally elicited sympathetic vasoconstrictor responses were examined in 12 patients with symptoms and signs of cardiovascular autonomic dysfunction due to Parkinson's disease. The sympathetic reflex mechanisms were measured in skeletal muscle and subcutaneous tissue of the arm and leg using the 133-Xenon washout technique. This method allows differentiation between local and central sympathetic reflexes in different tissues. The results indicate an abolished centrally mediated vasoconstrictor response in skeletal muscle in the arm and a decreased response in skeletal muscle in the leg and in subcutaneous tissue. This is in agreement with an autonomic dysfunction located in the central nervous system. A possible spinal sympathetic reflex controlling blood flow in subcutaneous tissue and leg muscles is considered. The sympathetic vasoconstrictor responses in parkinsonian patients without autonomic failure were of normal magnitude and the responses were not affected by long-term levodopa treatment.