脑干孤束核的应激调节机制

Adaptation of organisms to psychological stress includes a coordinated integration of behavioral and neuroendocrine (hypothalamo-pituitary-adrenocortical , HPA) responses. Stress adaption is critical to health and well-being of the organism, as behavioral and HPA axis hyperactivity have been implicated in the pathogenesis of depression and anxiety disorders. Thus, understanding the biology of this stress adaption system is critical to development of therapeutic or preventative strategies to combat HPA components of stress-related disease states..Behavioral and neuroendocrine responses to psychological stress are mediated by limbic-hypothalamic effector systems. In particular, the central amygdaloid nucleus (CeA) plays a major role in initiating behavioral responses to stressors (generation of fear/anxiety reactions), whereas the paraventricular nucleus (PVN) is the final common pathway controlling ACTH release. Whereas the effects of CeA and PVN activation are well-characterized, the neurocircuitry mediating upstream excitation of these systems remains to be defined. Our preliminary data suggest a prominent involvement of brainstem GLP-1-containing circuitry in mediating both behavioral and HPA responses to stress, respectively. Preproglucagon gene and protein expression are down-regulated by both acute and chronic variable stress (CVS) exposure, whereas the NTS noradrenergic gene and protein expression are enhance by CVS. As GLP-1 is only synthesized in the region of the NTS, our results indicate a preeminent role for the brainstem in subserving psychogenic stress responses initiated by limbic forebrain sites. These findings constitute a major revision of current thinking on brain stress integration mechanisms..In this proposal, we set out to tests the novel hypothesis that distinct brainstem neurons act as critical integrators of both stress habituation and sensitization, and are thereby responsible for adaptive as well as maladaptive hormonal and behavior responses by using rodent chronic stress models. We will determine 1) the role of NTS GLP-1 neurons in long-term stress adaptation by using NTS knockdown approach (lentiviral vectors); 2) whether noradrenergic neurons of the nucleus of the solitary tract (NTS) are responsible for driving HPA axis hyperactivity following chronic stress; 3) whether inappropriate drive of NTS noradrenergic neurons by forebrain stress-recruited pathway results in the neuroendocrine stress pathologies and behavior disorder. Successful completion of this proposal will add new insight into potential circuit pathology in affective disease, and provide novel molecular targets (GLP-1, brainstem glucocorticoid receptors) for development of therapeutic invention strategies.

抑郁和焦虑是现代社会中影响人类生活的情绪心理性疾病，神经通路在应激状态下的改变是造成抑郁和焦虑的生物学基础。在应激状态下，下丘脑-垂体-肾上腺轴（HPA轴）被迅速激活，使得机体产生包含行为和神经内分泌的协调整和的适应性行为。长期持续不可避免的应激引起个体行为（攻击，探究，睡眠，摄食和生殖行为）的改变并导致多种疾病，如抑郁和焦虑。我们的前期研究首次表明脑干孤束核对HPA轴在应激状体下的激活有重要的负反馈调制，这对理解抑郁焦虑的发病机理提供了新的思路和证据，但孤束核对HPA轴调节的神经通路和分子机制尚不清楚。本项目将利用抑郁和焦虑的动物模型，在前期研究工作的基础上研究脑干孤束核中肠促胰素（GLP-1）和去甲肾上腺素（NE）系统在应激状态下对HPA轴的调节机制和神经通路，以及脑干孤束核-大脑边缘系统-HPA轴的调控通路中的关键性因子，从而试图探索和发现潜在的治疗抑郁和焦虑的分子靶点。

目前为止，大量的研究集中在大脑皮层，边缘系统对心理性应激的神经通路研究，对于脑干部分，学界的共识是脑干部分更多参与生理性应激的调制，本课题在前期工作的基础上，预测脑干孤束核通过和下丘脑室旁核，杏仁核的双向投射而参与心理性应激的调控，本课题利用慢性应激动物模型以研究抑郁焦虑症的神经通路和神经内分泌变化。完成的具体内容见下：1）详细研究了脑干孤束核GLP-1系统和NE系统在急慢性应激中的调制机制和不同机理，以及可能对应的生理学意义；2）GLP-1和NE虽然都是作为可能的兴奋性神经递质和神经肽投射到下丘脑室旁核，但是在应激条件下二者的反应和作用却不一样，NE主要参与应激条件下的易化，从而保证即使在相同的应激刺激下，动物仍旧保有对外界刺激的反应而不是麻痹，从而保证动物的生存。而GLP-1体现了生物在慢性应激下的一种适应，从而保证生物的HPA轴对应激的反应控制在一定范围，避免过度反应而导致其他的不良影响，GLP-1系统和NE系统的平衡维持是一种生物适应性的进化机制，对于生物在外界各种应激刺激下的生存有重大意义；3）研究同时也表明 对于GLP-1系统和NE系统的调节是采取了不同的机制，慢性应激刺激下，glucocorticoids的升高很好的解释了动物在应激压力环境下的一种从正常到病理状态的反应，而GLP-1系统随着glucocorticoids的升高而降低，体现了一种负反馈抑制作用，NE系统的持续升高体现了神经递质有不受glucocorticoids调节的独立的机制；4）这种调节的多样性保证了动物对于不同的长期应激刺激的适应性平衡。研究结果提示脑干不仅参与急慢性生理和心理性应激的刺激，而且在孤束核同时启动GLP-1和NE系统的调节，这对于维持生物的平衡机制有重要意义；5）本研究脑干部分研究结果在继续整理发表中，除此之外，本研究课题进一步进行了脑干-下丘脑室旁核神经通路的研究，引入先进的区域性基因敲除技术，进一步阐明和脑干投射有关的室旁核CRH基因，HPA轴和glucocorticoids对于焦虑和抑郁的综合性调制。部分结果发表在Molecular Psychiatry上，文章发表后有媒体报道。