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Long-latency reflex activity in squirrel monkeys with occlusion of the middle cerebral artery
Abstract:
The primate middle cerebral artery (MCA) preparation has been studied as an animal model of human spasticity resulting from stroke. MCA occlusion in 3 squirrel monkeys was accomplished through a transorbital approach and animals were evaluated by 'clinical' examinations and studies of EMG responses to torque motor imposed joint displacement. Animals were transiently hemiparetic but not spastic postoperatively, although all were found to have a large infarct in MCA territory on post-mortem examination. The electromyographic (EMG) response of biceps in normal animals to torque motor imposed elbow extension consisted of both early (M1) and late (M2) components (Tatton et al. 1975). These components were unchanged following MCA occlusion. The EMG response to metacarpophalangeal joint extension in finger flexors or normal animals consisted solely of a long-latency (M2) component (Lenz et al. 1983a). Following MCA occlusion the M2 component in this muscle was decreased or absent, but a short-latency (M1) component appeared.
Insights
This study investigated middle cerebral artery (MCA) occlusion in squirrel monkeys as a stroke model. While not inducing spasticity, MCA occlusion altered electromyographic (EMG) responses in finger flexors, suggesting potential for studying motor control deficits.
Area of Science:
- Neuroscience
- Animal Models
- Stroke Research
Background:
- The primate middle cerebral artery (MCA) preparation is a model for stroke-induced spasticity.
- Understanding post-stroke motor impairments is crucial for developing effective therapies.
Purpose of the Study:
- To evaluate the utility of MCA occlusion in squirrel monkeys as an animal model for human spasticity.
- To investigate changes in electromyographic (EMG) responses following MCA occlusion.
Main Methods:
- Middle cerebral artery (MCA) occlusion was performed in 3 squirrel monkeys via a transorbital approach.
- Animals underwent clinical examinations and EMG response studies to torque motor-imposed joint displacement.
- Post-mortem examination confirmed infarcts in the MCA territory.
Main Results:
- Animals exhibited transient hemiparesis but not spasticity post-MCA occlusion.
- Biceps EMG responses (M1 and M2 components) remained unchanged after MCA occlusion.
- Finger flexor EMG responses showed a decreased or absent M2 component and an emergent M1 component post-MCA occlusion.
Conclusions:
- MCA occlusion in squirrel monkeys does not reliably induce spasticity.
- Alterations in EMG responses, specifically the emergence of an M1 component in finger flexors, suggest potential for modeling specific aspects of motor dysfunction after stroke.