Evaluation of the Role of the Noradrenergic System in Pain Perception in Parkinson's Disease

Patients suffering from Parkinson's disease (PD) frequently experienced painful sensations that could be, in part, due to a central modification of nociception mechanisms. Previous studies have shown that pain perception was altered in Parkinson's disease (subjective and objective pain thresholds and pain-induced cerebral activity) and that administration of L-Dopa normalized this alteration. In the central nervous system, L-Dopa is converted in dopamine and in norepinephrine. Apomorphine (a dopamine agonist) has no effect on pain threshold and pain-induced cerebral activity. Therefore the noradrenergic system could be involved in pain alteration in PD. To assess the role of noradrenergic system in pain in patients with PD, we chose duloxetine (norepinephrine and serotonin reuptake inhibitor)because a recent study had shown that duloxetine allowed an improvement of pain clinical scores (pain questionnaires) in patients with PD. 36 patients will be enrolled in this study. We supposed that a chronic intake of duloxetine increase the pain perception level compare to the placebo. This increase would be the same than those observed with L-Dopa.