Abstract: Objective To explore the relationship between levodopa-induced dyskinesia (LID) and phosphorylated extracellular signal-regulated kinase (ERK, Thr202/Tyr204, ERK1/2) in striatum. Methods The hemiparkinsonian rat model was produced by stereotaxically injecting 6-hydroxydopamine (6-OHDA) to right medial forebrain bundle (MFB). The hemiparkinsonian rats were intraperitoneally treated with levodopa (50 mg/kg) and benserazide (12.50 mg/kg) for 21 d and abnormal involuntary movement was evaluated. Immunofluorescent and Western blotting were used to observe the changes of phosphorylation of ERK1/2 in rat's striatum. Results Western blotting indicated that the 6-OHDA lesion induced a significant downregulation of the phosphorylation of ERK1/2 to (68.28 ± 7.42)% in comparison with the sham-lesioned group [ (107.05 ± 3.81)% ; t = 0.109, P = 0.018]. Chronic treatment with levodopa significantly increased the phosphorylation of ERK1/2 to (160.37 ± 10.54)% , which was compared to the Parkinson's disease (PD) group (t = 0.109, P = 0.000). The study of immunofluorescent staining revealed that there were few phosphorylation of ERK1/2 in the lesion side of hemiparkinsonian rats, and most of them were expressed in dynorphin-negative neurons; levodopa administration increased the phosphorylation of ERK1/2 expression compared with the PD group (t = 5.121, P = 0.000), and the co-expression of the phosphorylation of ERK1/2 and dynorphin increased to (83.62 ± 1.46)％ compared with PD group (t = 11.263, P = 0.003). Conclusion These results suggest that the changes of ERK1/2 phosphorylation state in the strionigral neurons can play an important role in the over-excitation of the direct pathway medium-spiny neurons.

Key words: Parkinson disease, Dyskinesia, drug-induced, Protein kinases, Fluorescent antibody technique, Levodopa

摘要： 目的 观察帕金森病运动并发症模型大鼠纹状体细胞外信号调节激酶（ERK）Thr202/Tyr204 位点（ERK1/2）磷酸化水平及表达位点的改变。方法 通过脑立体定向仪于大鼠内侧前脑束注射6-羟多巴胺建立帕金森病动物模型，连续腹腔注射左旋多巴（50 mg/kg）和苄丝肼（12.50 mg/kg）共21 d（2 次/d）以诱发运动并发症。通过Western blotting 法检测不同处理组大鼠纹状体磷酸化ERK1/2 表达水平，免疫荧光双标法观察磷酸化ERK1/2 与强啡肽共表达变化，以了解直接通路投射神经元ERK 磷酸化修饰情况。结果 Western blotting 检测显示，帕金森病组大鼠损伤侧纹状体磷酸化ERK1/2 表达水平为（68.28 ± 7.42）％，低于假手术组的（107.05 ± 3.81）%，组间差异具有统计学意义（t = 0.109，P = 0.018）；左旋多巴连续治疗21 d 后，表达水平升至（160.37 ± 10.54）％（t = 0.109，P = 0.000）。免疫荧光双标法检测，帕金森病组大鼠损伤侧纹状体区仅有（35.32 ± 5.03）％的磷酸化ERK1/2 与强啡肽共表达；经左旋多巴治疗后，共表达水平显著升至（83.62 ± 1.46）％，高于帕金森病组（t = 11.263，P = 0.003）。结论 长期应用左旋多巴可使帕金森病模型大鼠纹状体磷酸化ERK1/2 表达水平明显上调，且ERK 磷酸化多发生于直接通路投射神经元，提示黑质-纹状体投射神经元ERK 通路的活化可能参与了运动并发症的发生。

关键词: 帕金森病, 运动障碍, 药物性, 蛋白激酶类, 荧光抗体技术, 左旋多巴