Autonomic cardiovascular responses in parkinsonism: effect of levodopa with dopa-decarboxylase inhibition.

Autonomically mediated cardiovascular responses to certain manoeuvres were studied in 20 parkinson patients, 24 h off levodopa-decarboxylase inhibitor medication and again one h after medication. Results were compared with 15 healthy control subjects. The heart rate at rest was higher in parkinson, the respiratory sinus arrhythmia was lower, while the Valsalva ratio, the heart rate and blood pressure responses during an orthostatic test and the heart rate response to a dive reflex test were normal. These findings indicate a normal function of peripheral autonomic nerves and a possible central parasympathetic dysfunction. There were significantly attenuated responses of heart rate, blood pressure and contralateral forearm blood flow to an isometric handgrip. Since the peripheral autonomic nerves seemed to be normal, these results could be related to a reduced central command and/or diminished stimulation of postulated peripheral ergoreceptors in parkinsonism. There was no major effect on the cardiovascular responses by the acutely administered medication.