前扣带回皮质影响内侧前额叶皮质兴奋性调节晕动病的神经环路和机制

We observed previously that prelimbic and infralimbic cortices (PrL and IL, respectively), the two important components of medial prefrontal cortex, were simultaneously excited by activation of anterior cingulate cortex (ACC), which mediated the role of ACC in facilitating motion sickness (MS). The mechanisms therein, however, remain unclear. In this project, we propose, utilizing modern neuroscience techniques such as opto-/chemogenetic approaches, immunoelctron microscopy, immunoflurescence, patch clamp and extracellular recording techniques, to carry out the following experiments which, after being performed smoothly and successfully, will provide valuable results of the theorectical basis for fully understanding the neural mechanisms underlying MS development and for developing new anti-MS strategies. The related studies involves (1) investigation into the characteristics of MS development associated with the activities of the pathway, “ACC-PrL/IL-nucleus of solitary tract”, as will be parsed by perturbation of the pathway by using opto-/chemogenetic approaches; (2) unveiling, at the cellular level, neural connections between ACC and MS related neurons in PrL/IL, as well as the local circuits structured by distinct GABAergic neuron types and the signal processing modes employed by these GABA neurons, as will be disclosed through selectively labeling the GABAergic and MS-related neurons in PrL and IL on genetically modified animals such as GAD67-GFP、gad2-cre mice; (3) investigating how the MS-related neurons in PrL/IL are electrically excited and the related cellular mechanisms whereby these MS-related neurons integrate and process the excitatory and inhibitory signals from ACC and local GABAergic neurons, respectively.

我们观察到属于内侧前额叶皮质的边缘前皮质（PrL） 和边缘下皮质（IL）可被前扣带回皮质（ACC）同时兴奋，参与ACC对晕动病（MS）的易化作用，其中的神经机制不清楚。本项目拟综合运用光/化学遗传学、免疫（电镜）染色以及脑片膜片钳等技术，进行以下研究，以期为全面理解MS发生和调控的神经机制、研发新型抗MS策略奠定理论基础：（1）干扰“ACC-PrL/IL-孤束核”神经通路活动，分析该通路影响MS的规律和特点；（2）采用GAD67-GFP、gad2-cre等遗传修饰动物，选择性标记PrL/IL内GABA能和MS相关神经元，在细胞水平解析神经信号经ACC“流向”PrL/IL内MS相关神经元的纤维联系模式、不同类型GABA能神经元构成的局部环路及其调节MS相关神经元兴奋性的方式；（3）研究PrL/IL 内MS相关神经元对来自ACC和GABA能神经元的兴奋和抑制性信号的加工、整合及其被兴奋的机制。

前扣带回皮质（anterior cingulate cortex, ACC）与内侧前额叶皮质（medial prefrontal cortex, mPFC）两个脑区在接受前庭刺激后，发生兴奋性活动“偶联”并参与对晕动病（motion sickenss, MS）的调节，但其神经机制尚不清楚。项目通过多种技术手段，证明了ACC、mPFC参与调节MS的功能并研究了ACC和mPFC之间的神经联系通路。.截止目前，研究结果和内容主要集中在以下三个方面。第一，证明前庭信息传入可以激活ACC和mPFC两个脑区。这一结果与我们既往电生理学研究显示的旋转刺激促使上述两脑区神经元放电增强的数据相互支持。接着用行为学技术揭示了这两个脑区在参与前庭信息加工同时，具有促进MS发病的功能。第二，研究了ACC与mPFC之间的投射通路。具体而言，ACC （以及中缝背核dorsal raphe, DR）内接受前庭信号的神经元大多数都与mPFC内的兴奋性神经元发生纤维联系，只有很少量ACC和DR神经元调节mPFC内GABA能神经元兴奋性活动。第三，旋转运动选择性激活DR尾侧的神经元。具体而言，只有DR中、尾段的神经元对旋转运动刺激有反应，而DR吻段对前庭刺激无明显反应。继之用电损毁技术，证明DR核团的中、尾段5-HT能神经元的兴奋性活动对晕动病发生有易化作用，但对动物正常运动行为无影响。.项目研究证明ACC、mPFC两个大脑皮质区接受、处理前庭信号，两脑区都有易化晕动病的功能。这一研究发现在国内外尚未见报道，创新性较强。此方面的研究不但从解剖学角度拓展了人们对传统脑区ACC、mPFC功能的认识，而且对把晕动病的研究方向引导至对高级脑结构调控晕动病的机制探讨方面有着重要作用。此外，该项目研究显示ACC、mPFC两个脑区可协同性的被前庭信号兴奋，ACC神经元可单突触地兴奋mPFC中的兴奋性神经元（CaMKII阳性）和GABA能神经元，但是ACC神经元对GABA能神经元的单突触支配十分稀少。这一结果可部分解释ACC、mPFC两脑区易化MS调节的神经机制，这在探讨高级脑区调控MS的机制研究方面属于领先研究。最后，我们指出DR中、尾段选择性被前庭信号激活从而促进MS，该研究结果在国内外尚未见报道，显示了研究的先进性。