脑内褪黑素在帕金森病发生发展中的动态变化及其作用

Parkinson's disease (PD) is an age-related, progressive, multisystem neurodegenerative disorder. Classically, the hallmark of PD is loss of dopaminergic neurons of the substantia nigra pars compacta, leading to bradykinesia, rigidity and tremor. Nowadays there is considerable evidence showing that non-dopaminergic degeneration also occurs in other brain areas which seems to be responsible for the deficits in olfactory, emotional and memory functions that precede the classical motor symptoms in PD. So far, the cause of the disease is unknown. Several published articles have documented that melatonin effectively protects against the degeneration of dopaminergic neurons in PD models. However, we have recently reported that the concentrations of melatonin at day and night in both eyes were distinctly increased compared with the vehicle groups in rat model of advanced PD. Similarly, the level of melatonin in the striatum dialysates of same PD model was increased as well in our preliminary experiment. Therefore, we proposed that melatonin might play dual roles in PD progression. In the following study, brain microdialysis combined with HPLC method will be applied to monitor the extracellular levels of melatonin and dopamine in the striatum dialysates of freely moving rats in 6-OHDA induced model of PD. Also, we will detect the distribution and change of melatonin receptors in substantia nigra and striatum by RT-PCR, Western blot and immunochemistry in different stages of rat model of PD, and provide a new understanding of the relationship of melatonin receptors and dopamine. The results will contribute to the understanding of pathogenic mechanisms of PD and to provide new treatment strategies or discovery a new biomarker in different stage of PD.

帕金森病（Parkinson's Disease，PD）是一种与年龄相关的进行性、多系统神经退行性紊乱，主要导致运动障碍及痴呆、睡眠障碍等非运动症状，其发病机制未明。大量研究显示，褪黑素可缓解PD动物黑质多巴胺神经元的死亡。但本项目前期研究发现，中晚期PD大鼠视网膜褪黑素的昼夜水平均明显高于对照组，同期PD大鼠纹状体透析液的预实验也存在类似结果。据此，我们提出褪黑素很可能在PD进展中发挥双重作用的假说。拟以褪黑素与多巴胺之间的关系为主线，建立6-OHDA诱导的PD模型大鼠，用脑微透析术和HPLC动态监测纹状体透析液褪黑素及多巴胺的变化。结合褪黑素受体拮抗剂，通过神经生化、组织学、分子生物学和行为学等方法，检测脑内褪黑素受体的分布及变化，以及这些变化与多巴胺之间的关系。研究结果将初步阐明褪黑素在PD进程中的潜在作用，为进一步寻找潜在的PD治疗靶点或发现PD不同进程的生物标志物提供理论依据。

本课题组以褪黑素与多巴胺之间的关系为主线，建立6-羟基多巴胺（6-hydroxydopamine，6-OHDA）诱导的偏侧帕金森病（Parkinson’s disease, PD）模型大鼠，用脑微透析术和HPLC动态监测纹状体透析液褪黑素（melatonin, MLT）及多巴胺（dopamine, DA）的变化。通过神经生化、组织学、分子生物学和行为学等方法，检测脑内褪黑素及其受体的变化，以及这些变化与多巴胺之间的关系，探讨PD发生发展中褪黑素变化的机制，期望为临床更有效地治疗PD提供新的思路或发现PD不同进程的生物标志物奠定基础。结果表明，PD组毁损侧纹状体10:00和22:00 DA及其代谢产物DOPAC与HVA水平明显低于对照组或PD组健侧；PD组毁损侧纹状体MLT与DA变化存在相关性，同时PD组毁损侧纹状体DA和MLT变化与动物旋转行为也存在相关性。PD组毁损侧纹状体组织MLT受体MT1和MT2表达明显低于对照组或PD组健侧。结果提示：6-OHDA诱导的偏侧PD大鼠毁损侧纹状体显著增加的MLT水平可能与PD的进展有关。.研究成果：发表论文：.1、杜越群，孟涛，郑志竑，林玲，6-羟基多巴胺诱导的帕金森病大鼠纹状体5-羟吲哚乙酸和褪黑素水平及与多巴胺的关系。中华行为医学与脑科学杂志，2013；22（4）:293-295..2、Lin L, Du Y, Yuan S, Shen J, Lin X, Zheng Z. Serum melatonin is an alternative index of Parkinson's disease severity. Brain Res. 2014; 1547: 43-48. pii: S0006-8993(13)01592-8. doi: 10.1016/j.brainres.2013.12.021.