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Characterisation of dyskinesias induced by L-dopa in MPTP-treated squirrel monkeys
S Boyce1, N M Rupniak, M J Steventon
1Merck Sharp and Dohme Research Laboratories, Neuroscience Research Centre, Harlow, Essex, UK.
Abstract:
Intermittent treatment with L-dopa over a 2-year period induced abnormal involuntary movements in MPTP-treated squirrel monkeys. Dyskinesias included a choreic and dystonic component. Dose-response curves for chorea and dystonia revealed that the same dose of L-dopa (30 mg/kg) induced the highest score for both dyskinesias: however, the severity was much greater for chorea. Choreic movements were always most prevalent at the time of peak effect, whereas dystonia was apparent at the time of peak effect and at "end-of-dose", and was occasionally observed spontaneously. Our findings indicate that squirrel monkeys treated with MPTP develop L-dopa-induced dyskinesias which closely resemble those observed in Parkinson's disease. This species provides a valuable animal model to develop improved therapeutic agents.
Insights
Squirrel monkeys treated with MPTP developed L-dopa-induced dyskinesias, closely resembling Parkinson's disease. This finding highlights the squirrel monkey as a valuable model for studying and developing treatments for these movement disorders.
Area of Science:
- Neuroscience
- Pharmacology
- Primate Models
Background:
- Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor deficits.
- Levodopa (L-dopa) is a primary treatment for PD, but its long-term use can lead to motor complications like dyskinesias.
- MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) is a neurotoxin that causes parkinsonism in various animal models.
Purpose of the Study:
- To investigate the development of L-dopa-induced dyskinesias in MPTP-treated squirrel monkeys.
- To characterize the nature and temporal patterns of these dyskinesias.
- To evaluate the utility of this primate model for preclinical therapeutic development.
Main Methods:
- Squirrel monkeys were treated with MPTP to induce parkinsonism.
- Intermittent L-dopa treatment was administered over a 2-year period.
- Abnormal involuntary movements (dyskinesias) were assessed, including choreic and dystonic components, and dose-response relationships were analyzed.
Main Results:
- Intermittent L-dopa administration induced abnormal involuntary movements in MPTP-treated squirrel monkeys.
- Dyskinesias presented with both choreic and dystonic features.
- The dose of 30 mg/kg L-dopa produced the highest scores for both chorea and dystonia, with chorea being more severe.
- Choreic movements peaked with L-dopa effect, while dystonia occurred at peak effect, end-of-dose, and spontaneously.
Conclusions:
- MPTP-treated squirrel monkeys exhibit L-dopa-induced dyskinesias that closely mimic those seen in Parkinson's disease patients.
- This animal model is suitable for studying the pathophysiology of L-dopa-induced dyskinesias.
- The squirrel monkey model offers a valuable platform for developing and testing novel therapeutic strategies for dyskinesias in PD.