title: Abnormal bidirectional plasticity-like effects in Parkinson's disease.
abstract: Levodopa-induced dyskinesia is a major complication of long-term dopamine replacement therapy for Parkinson's disease that becomes increasingly problematic in advanced Parkinson's disease. Although the cause of levodopa-induced dyskinesias is still unclear, recent work in animal models of the corticostriatal system has suggested that levodopa-induced dyskinesias might result from abnormal control of synaptic plasticity. In the present study, we aimed to explore control of plasticity in patients with Parkinson's disease with and without levodopa-induced dyskinesias by taking advantage of a newly developed protocol that tests depotentiation of pre-existing long-term potentiation-like synaptic facilitation. Long-term potentiation-like plasticity and its reversibility were studied in the motor cortex of 10 healthy subjects, 10 patients with Parkinson's disease and levodopa-induced dyskinesias, who took half of the regular dose of levodopa and 10 patients with Parkinson's disease without levodopa-induced dyskinesias, who took either half or the full dose of levodopa. Patients with Parkinson's disease without levodopa-induced dyskinesias had normal long-term potentiation- and depotentiation-like effects when they took their full dose of levodopa, but there was no long-term potentiation-like effect when they were on half dose of levodopa. In contrast, patients with levodopa-induced dyskinesias could be successfully potentiated when they were on half their usual dose of levodopa; however, they were unresponsive to the depotentiation protocol. The results suggest that depotentiation is abnormal in the motor cortex of patients with Parkinson's disease with levodopa-induced dyskinesias and that their long-term potentiation-like plasticity is more readily affected by administration of levodopa than their clinical symptoms.
authors: Department of Neurology, Chang Gung Memorial Hospital, Taipei 10507, Taiwan.
authors: Ying-Zu
authors: YZ
authors: Huang
authors: John C
authors: JC
authors: Rothwell
authors: Chin-Song
authors: CS
authors: Lu
authors: Wen-Li
authors: WL
authors: Chuang
authors: Rou-Shayn
authors: RS
authors: Chen
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D000978:Antiparkinson Agents / Q000009:adverse effects / Q000494:pharmacology; D004409:Dyskinesia, Drug-Induced / Q000473:pathology*; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D007980:Levodopa / Q000009:adverse effects / Q000494:pharmacology; D036881:Long-Term Synaptic Depression / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009119:Muscle Contraction / Q000187:drug effects; D010300:Parkinson Disease / Q000188:drug therapy / Q000473:pathology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa