Objective: We aimed to clarify the relationships between the alpha-synuclein level and abnormal oscillatory activity and their changes induced by deep brain stimulation of the substantia nigra.

Background: A recent study suggested that abnormal oscillatory activity is related to the pathogenesis of Parkinson’s disease (PD). Deep brain stimulation improves motor complications by modulating abnormal oscillatory activity. Furthermore, a recent animal study also suggested that the activation of neuronal activity increases alpha-synuclein levels. Although abnormal oscillatory activity and alpha-synuclein levels might probably contribute to the pathogenesis of PD, the relationships between the abnormal oscillatory activity and alpha-synuclein levels are unknown.

Method: Experiments were conducted under urethane anesthesia in normal Sprague–Dawley rats (n=4). We stereotaxically inserted a microdialysis probe attached to a tungsten electrode into the substantia nigra. We collected extracellular fluid and recorded local field potential pre, during, and post-stimulation of substantia nigra. Electrical stimulation of the substantia nigra was performed using the same tungsten electrode. We calculated the power of delta, theta, alpha, and beta frequency from the recorded local field potential. We measured the alpha-synuclein level by enzyme-linked immunosorbent assay (ELISA). We calculated the ratio to the basal levels of alpha-synuclein levels in the substantia nigra with respect to the stimulation phase.

Results: The alpha-synuclein levels in substantia nigra slightly increased to 1.43±0.32 during stimulation compared to pre-stimulation without statistical significance (p=0.966). The alpha-synuclein levels significantly increased to 2.16±0.48 post-stimulation compared to pre-stimulation. With respect to the relationships between the oscillatory activity and the alpha-synuclein levels, weak negative correlations were found between the power of delta, theta, alpha, and beta frequency and the alpha-synuclein levels pre, during, and post-stimulation without statistical significance.

Conclusion: The alpha-synuclein levels in the substantia nigra significantly increased after electrical stimulation of the substantia nigra. Weak negative correlations might exist between the alpha-synuclein levels and the power of oscillatory activity which needs further examination.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-changes-in-alpha-synuclein-level-and-oscillatory-activity-of-substantia-nigra-by-nigral-electrical-stimulation/