多巴胺神经元调控工作记忆的神经环路机制的研究

Working memory is a process of temporary information maintain and manipulation, which provides the stability necessary for cognition. It is indicated that dopamine is crucial for working memory by pharmacological experiments. Our recent studies suggest that enhance or suppress the activities of dopaminergic neurons in ventral tegmental area (VTA) can increase or decrease the behavioral performance of mice in working memory task. Moreover, the behavioral performance is decreased by the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which is a neurotoxin to selectively damage the dopaminergic neurons. However, the mechanism of neural circuits of dopaminergic neuron in working memory is unclear. We have proved that mPFC neuron activity during the delay period is important for learning in working memory task, and confirmed that the functional role of mPFC is memory storage. Therefore, on this basis, we propose to focus on mPFC and use optogenetic method, fiber photometry and extralcelluler recording techniques to illustrate how the dopaminergic neurons regulate mPFC neuron activities related to working memory. Furthermore, in view of the different cell-types, we also investigate the functional role of dopaminergic neurons in the local circuit for working memory using optogenetic method, two-photon calcium imaging and extralcelluler recording techniques. This project aims to reveal the mechanism of neural circuits of dopaminergic neuron in VTA for working memory process. The success of this project will provide a new idea of clinic diagnosis for dopamine-related diseases such as Parkinson’s disease.

工作记忆是大脑在线、实时存储和操作信息的过程，在认知行为中占核心地位，药理学手段表明多巴胺在工作记忆行为中起着重要作用。本课题前期实验中，利用光遗传手段双向调控腹侧被盖区（VTA）多巴胺能神经元活动，可以双向调节工作记忆行为的正确率；同时应用对多巴胺能神经元有特异性作用的神经毒素1-甲基-4-苯基-1，2，3，6-四羟基嘧啶（MPTP）的在体药理学手段，证明工作记忆行为的正确率被显著降低。但多巴胺能神经元调控工作记忆的神经环路机制不明。基于此，我们综合利用光遗传、双光子钙成像、光纤钙成像、胞外电生理记录等多种技术，聚焦内侧前额叶皮层（mPFC），阐明多巴胺能神经元如何调控mPFC工作记忆相关的神经元活动，并针对不同类型的神经元，解析多巴胺能神经元对工作记忆调控的局部神经环路机制。本课题将初步揭示VTA多巴胺神经元调控工作记忆的神经环路机制，并为多巴胺相关疾病如帕金森氏症，提供诊断的新思路。

工作记忆是大脑在线、实时的存储和操作信息的过程，是知觉、长时记忆和动作之间的接口，在认知行为中占据核心地位。帕金森病 (Parkinson’s disease, PD)、精神分裂症、抑郁障碍等很多神经系统疾病都被认为存在工作记忆障碍。PD是一种常见的神经退行性疾病，病理表现为黑质-纹状体通路多巴胺能神经元的缺失，临床上以运动障碍、静止时震颤、僵直、步态异常为特征，但其发病机制尚不明确。90%的PD患者在运动障碍之前的几年甚至十几年会出现嗅觉障碍，且随着疾病的发展，嗅觉障碍越来越严重，因此研究嗅觉障碍的病理机制，将对临床提早诊断和治疗PD有指导意义。已有研究表明，PD患者的气味识别障碍出现得比气味鉴别障碍更早，提示可能是气味记忆首先受到损伤，而其神经环路机制目前还不清楚，是脑科学亟待解决的关键问题之一。实验室自行开发的让限水的小鼠头部固定完成嗅觉工作记忆任务，在实验中我们发现，MPTP诱导的PD模型小鼠存在嗅觉工作记忆障碍，且出现在行为障碍之前；接着，我们利用PD转基因小鼠，证明嗅觉工作记忆行为的正确率被显著降低，且此时，小鼠尚未出现运动障碍，之后我们继续监测小鼠运动能力，数月过后，才出现小鼠的运动能力逐渐下降的现象，这与人的PD临床病情发展过程类似；之后，我们通过激活内侧前额叶皮层（mPFC）-无颗粒岛叶皮层（aAIC）神经环路，改善了小鼠的嗅觉工作记忆行为损伤；此外，我们利用电生理技术，聚焦mPFC-aAIC神经环路，探讨在PD小鼠的神经机制；阐释了PD早期发病机制，为提早诊断和治疗PD提供新思路和理论支持。