高頻刺激視丘下核活化巴金森氏模式鼠的運動皮質

High-Frequency Stimulation of the Subthalamic Nucleus Activates Motor Cortex in Hemi-Parkinsonian Rats

莊季芬(Chi-Fen Chuang)

指導教授 ： 張兗君

國立清華大學/生命科學院/分子醫學研究所/博士(2018年)

摘要

巴金森氏症是全球僅次於阿茲海默症第二常見的神經退化性疾病。在本研究中，我們利用藥物單邊破壞大鼠單邊中腦區的多巴胺神經元的hemi-Parkinsonian 大鼠作為模式生物，藉由測量清醒未麻醉且自由活動之hemi-Parkinsonian 大鼠腦內主要運動皮質（primary motor cortex，M1）的腦內區域活性訊號（Local field potential），我們可發現一些與正常大鼠腦內區域活性訊號的不同之處，主要是強烈的beta oscillation 及大量出現的High voltage spindles（HVSs）腦波訊號。
深層腦刺激（DBS）是廣泛被用於改善嚴重巴金森氏症的治療方法，本篇利用視丘下核腦區（STN）133赫茲的高頻刺激 (簡稱STN-HFS) 模擬腦深層刺激。然而這些不正常的訊號能夠藉由給予hemi-Parkinsonian大鼠STN-HFS而降低beta oscillation強度與HVSs的出現頻率。STN-HFS甚至能抑制常用來斷定大鼠為hemi-Parkinsonian 模式鼠的甲基安非他命所誘發之同側旋轉行為。
為了探討視丘下核深層腦刺激對運動皮質神經活性的影響，我們記錄M1的第二、三層與第五層（M1-layer II/III與M1-layer Vb）在施予STN-HFS時所被誘發的腦內活性訊號(evoked potentials, EPs)，其誘發的腦內活性訊號根據推測分別主要因為溯回spike (antidromic spike) 及區域活性訊號(local activity)。本實驗發現於M1 的第II/III層處理CNQX及Bicuculin 用以分別抑制GABA及Glutamate神經元的神經間的傳遞能夠有效降低高頻刺激誘發的皮質區域腦部活性，但而沒辦法降低刺激同側刺激視丘下核後於M1產生的溯回spike。
研究常利用c-Fos的表現常做為神經活性的指標，我們發現到hemi-Parkinsonian大鼠的左右半腦運動皮質中c-Fos表現細胞的數量是不一致的，而這種不一致的
現象是能夠經由STN-HFS而矯正的。此外，STN-HFS會使運動皮質的某群細胞產生強烈的c-Fos表現，這些細胞的生化及結構上都與椎狀細胞（pyramidal cell）相符合並具有傳出的神經軸突至視丘下核特性。我們亦發現這些錐狀細胞的強烈c-Fos表現能夠受到局部的給予運動皮質淺層對非NMDA的Glutamate、GABAa及多巴胺受體之拮抗劑抑制。此結果顯示出STN-HFS會同時活化運動皮質的神經突觸與多巴胺受器，進而造成強烈的c-Fos表現的原因。錐狀細胞的c-Fos的強烈表現也反映出在深層腦刺激時的細胞處於活化狀態。本研究也進一步探討視丘下核深層腦刺激後運動皮質中的多巴胺受體如何被活化以及運動皮質中的多巴胺受體活化後對巴金森氏症的治療效果的貢獻。

關鍵字

腦深層刺激 ； 多巴胺受器 ； 運動皮質 ； 巴金森氏症 ； 視丘下核

並列摘要

Parkinson’s disease (PD) is the second most common debilitating neurologic disease after Alzheimer’s disease globally. In this study, rats whose midbrain dopaminergic neurons have been depleted unilaterally, called as hemi-Parkinsonian rats, are used as a model. By local field potential (LFP) recording, we detect alterations in the activities in the primary motor cortex, M1, of freely moving hemi Parkinsonian rats. These alterations include the presence of exacerbated oscillations in the β‐regime and the more frequent appearance of high voltage spindle episodes (HVSs). Application of high-frequency, 130 Hz, stimulation applied on the subthalamic nucleus (STN-HFS) is used to mimic the DBS treatment that is widely used to treat advanced Parkinson’s disease. Application of STN-HFS in hemi-Parkinsonian rats can also attenuate the β-oscillations and reduce the appearance of HVSs, as well as reverse the amphetamine-induced rotation, which is a characteristic movement of these rats.
Here, we investigate how STN-HFS influences the neural activity in the motor cortex. During the interval between two consecutive stimulations, evoked LFPs corresponding to antidromic spikes and local activities are recorded in layer II/III and layer Vb regions of the M1. Local application of CNQX and bicuculline, which respectively inhibit fast glutamatergic and GABAergic synaptic transmission, in layer II/III, but not layer V of M1 greatly reduces the local activity, but not the activity corresponding to antidromic spikes induced by STN-HFS to the same side.
c-Fos expression in neurons is used as an indicator of neural activity. We find that the motor cortices in the two hemispheres of hemi-Parkinsonian rats contain unequal number of c-Fos+-cells, and STN-HFS rectifies this bilateral imbalance. In addition, STN-HFS leads to the intense c-Fos expression of a group of motor cortex neurons which exhibit biochemical and anatomical characteristics resembling those of pyramidal tract (PT) neurons sending efferent projections to the STN. The number of PT neurons whith high levels of c-Fos expression is significantly reduced by local application of the antagonists to non-NMDA glutamate receptors, GABAA receptors and dopamine receptors in the upper layers of the motor cortex. The results suggest that the coincident activations of synapses and dopamine receptors in the motor cortex during STN-HFS may underlie the intense expression of c-Fos, which reflects the status of neuronal activity, of PT neurons. How dopamine receptors in the motor cortex are activated during STN-HFS and how dopamine receptor activation in the motor cortex may contribute to the therapeutic effects of STN-DBS in treating PD have also been discussed.

並列關鍵字

deep brain stimulation ； dopamine receptors ； motor cortex ； Parkinson’s disease ； subthalamic nucleus

參考文獻

Alexander, G.E., DeLong, M.R., and Strick, P.L. (1986). Parallel organization of functionally segregated circuits linking basal ganglia and cortex. Annual review of neuroscience 9, 357-381.

Awenowicz, P.W., and Porter, L.L. (2002). Local application of dopamine inhibits pyramidal tract neuron activity in the rodent motor cortex. Journal of neurophysiology 88, 3439-3451.

Baker, K.B., Montgomery, E.B., Jr., Rezai, A.R., Burgess, R., and Luders, H.O. (2002). Subthalamic nucleus deep brain stimulus evoked potentials: physiological and therapeutic implications. Movement disorders : official journal of the Movement Disorder Society 17, 969-983.

Beaulieu, J.M., Espinoza, S., and Gainetdinov, R.R. (2015). Dopamine receptors - IUPHAR Review 13. Br J Pharmacol 172, 1-23.

Beck, M.H., Haumesser, J.K., Kuhn, J., Altschuler, J., Kuhn, A.A., and van Riesen, C. (2016). Short- and long-term dopamine depletion causes enhanced beta oscillations in the cortico-basal ganglia loop of parkinsonian rats. Experimental neurology 286, 124-136.