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

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.