title: Effect of levodopa on pain threshold in Parkinson's disease: a clinical and positron emission tomography study.
abstract: Patients suffering from Parkinson's disease (PD) frequently experienced painful sensations that could be in part due to central modification of nociception. We compared pain threshold before and after administration of levodopa in PD patients and in controls, and investigated cerebral activity with positron emission tomography (PET) during experimental nociceptive stimulation. Pain threshold was determined using thermal stimulation during two randomized conditions: off and on. We performed H(2) (15)O PET analysis of regional cerebral blood flow on subjects while they received alternate randomized noxious and innocuous stimuli during off and on conditions. In off condition, pain threshold in nine PD patients was significantly lower than in nine controls. Administration of levodopa significantly raised pain threshold in PD patients but not in controls. During off condition, there was a significant increase in pain-induced activation in right insula and prefrontal and left anterior cingulate cortices in PD compared to control group. Levodopa significantly reduced pain-induced activation in these areas in PD. This study shows that pain threshold is lower in PD patients but returns to normal ranges after levodopa administration. Moreover, PD patients have higher pain-induced activation in nociceptive pathways, which can be reduced by levodopa.
authors.affiliation: Service de Pharmacologie Clinique, University Hospital, Toulouse, France. brefel@cict.fr
authors.forename: Christine
authors.initials: C
authors.lastname: Brefel-Courbon
authors.forename: Pierre
authors.initials: P
authors.lastname: Payoux
authors.forename: Claire
authors.initials: C
authors.lastname: Thalamas
authors.forename: Fabienne
authors.initials: F
authors.lastname: Ory
authors.forename: Isabelle
authors.initials: I
authors.lastname: Quelven
authors.forename: François
authors.initials: F
authors.lastname: Chollet
authors.forename: Jean Louis
authors.initials: JL
authors.lastname: Montastruc
authors.forename: Olivier
authors.initials: O
authors.lastname: Rascol
mesh_terms: D000368:Aged; D000978:Antiparkinson Agents / Q000627:therapeutic use*; D001931:Brain Mapping; D016022:Case-Control Studies; D002540:Cerebral Cortex / Q000098:blood supply; D002560:Cerebrovascular Circulation / Q000187:drug effects; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use*; D008875:Middle Aged; D010146:Pain / Q000188:drug therapy / Q000209:etiology; D018710:Pain Clinics; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000187:drug effects*; D010300:Parkinson Disease / Q000188:drug therapy* / Q000503:physiopathology; D049268:Positron-Emission Tomography
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa