Circadian secretion pattern of melatonin in de novo parkinsonian patients: evidence for phase-shifting properties of l-dopa.

Aim of this study was the characterization of the circadian melatonin profile in de novo Parkinson patients (N = 9, age 60.0 +/- 3.2 years, mean +/- SEM) and the comparison of these profiles with those of controls and Parkinson patients treated with l-dopa/decarboxylase inhibitor (l-dopa/DCI). We collected 14 venous blood samples during a period of 24 hours and measured the serum melatonin levels by a radioimmuno assay. De novo Parkinson patients displayed the nocturnal melatonin peak (acrophase) at the same time as controls and significantly later than l-dopa/DCI treated patients (1:54 +/- 15.6 min [average clock time +/- SEM in minutes] vs. 1:45 +/- 15.6 min vs. 0:13 +/- 40.8 min). The amount of secreted melatonin did not differ among the three groups. Stage and duration of Parkinson's disease did not correlate with the amount of secreted melatonin. Patients of the tremor subgroup, however, secreted more melatonin than patients presenting only with rigidity and akinesia. The phase advance in Parkinson patients treated with l-dopa/DCI is possibly due to a central nervous dopaminergic effect elicited by l-dopa administration and not inherent to Parkinson's disease per se.