Cardiovascular reflexes in Parkinson's disease: long-term effects of levodopa treatment on de novo patients

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Abstract
Twelve parkinsonian patients (6 men and 6 women), mean age 60.5 years, range 47-72, were examined with autonomic test when de novo and after 2 years of continuous levodopa treatment. They were all free from any disease interfering with autonomic examination. When de novo they had a significant decrease of heart rate response to deep breathing and to laying to standing tests if compared with an age- and sex-matched control group (15.6 .+-. 8.8 vs. 28.6 .+-. 12.1, P < 0.01 and 7.0 .+-. 7 vs. 14.2 .+-. 5, P < 0.01). After 2 years of levodopa treatment they had a non-significant decrease of heart rate response to deep breathing test (21.8 .+-. 10.6, P N.S.) and a still significant decrease of heart rate response to laying to standing test, but at a lesser level (7.7 .+-. 7.0 P < 0.05). Furthermore, they showed a significant decrease of the systolic and MAP orthostatic pressure to tilting table (-9.2 .+-. 12.0 vs. +4.9 .+-. 8.9 and -4.5 .+-. 8.4 vs. +4.7 .+-. 5.1, both P < 0.01) probably due to medication. The other tests were never significant. We hazard as possible explanation an action of levodopa on dopaminergic neurons in the nucleus dorsalis of vagus.