Balancing motivation through VTA GABA/Glutamate co-transmission

项目总结 识别内环境平衡和失控动机背后的神经回路机制是 对开发更有针对性和有效的治疗神经精神障碍至关重要，如 严重的抑郁症或双相情感障碍。在边缘中脑奖赏回路中，腹侧被盖区 (VTA)是奖励和厌恶的主要调节因素。虽然通常会减少到它的多巴胺投射 神经元，VTA也含有共同释放抑制性GABA和兴奋性谷氨酸等的神经元 对多巴胺的投射，可以调节动机。然而，这种GABA/谷氨酸联合的功能作用- 发布仍然没有被很好地理解，关于它们在积极与消极中的作用的主要问题 增援依然存在。特别是，为什么神经元会同时发出抑制性和兴奋性信号 有信号吗？这组拟议的实验将系统地检验VTA GABA/谷氨酸共同- 释放是一种平衡突触后活动和动力的机制，以一种稳态的方式。 利用光遗传学驱动VTA、GABA/谷氨酸在下游结构中共同释放，这些结构调节情绪和 动机，我将应用基因编辑工具(CRISPR/Cas9)来测试GABA与 行为强化中的谷氨酸释放(目标1)。然后我将应用化学遗传学方法和慢性 改变突触后活动的行为操作以测试光遗传驱动的体内净效应 VTA、GABA/谷氨酸的体内钙成像共释放(目标2)。这些实验将揭示基本的 神经递质共释放的机制及其在平衡中脑边缘回路中的作用 与极端相关的传出结构的动机和防止长时间的兴奋/抑制 激励状态。GABA/谷氨酸共释放使活性正常化的能力可以提供一种新的 用于治疗动机不平衡的障碍，如双相情感障碍或抑郁症。一个坚强的人 由教师导师和专家组成的跨学科团队将提供所需的科学培训 拟议的实验(基因编辑和纤维光度测定)以及职业发展培训，以 促进成功过渡到本计划书的R00阶段。在R00阶段，我将统一我的之前 用新获得的技能来确定新描述的 VTA、GABA/谷氨酸投射至杏仁核。使用活体钙成像，我将首先监测VTA的活动 在基于努力的仪器蔗糖任务中杏仁核中的GABA/谷氨酸终末，然后将识别 光遗传刺激VTA-GABA/谷氨酸终末对细胞定义的杏仁核的净效应 人口(目标3)。这些结果将极大地扩展我们对VTA共释放在 复杂的动机行为与双相情感障碍和抑郁的模型相关，并将至关重要地为 为更有针对性的方法铺平道路，这是我独立研究计划的基础。

PROJECT SUMMARY Identifying the neural circuit mechanisms underlying both homeostatic and uncontrolled motivation are crucial for developing more targeted and effective therapeutic treatments for neuropsychiatric disorders like major depression or bipolar disorder. Within mesolimbic brain reward circuitry, the ventral tegmental area (VTA) is a major regulator of both reward and aversion. While generally reduced to its dopamine projection neurons, the VTA also contains neurons that co-release inhibitory GABA and excitatory glutamate and, similar to dopamine projections, can modulate motivation. However, the functional role of this GABA/glutamate co- release is still not well understood, and major questions regarding their role in positive vs. negative reinforcement remain. In particular, why would neurons simultaneously send an inhibitory and excitatory signal? This set of proposed experiments will systematically test the hypothesis that VTA GABA/glutamate co- release serves as a mechanism to balance postsynaptic activity and motivation in a homeostatic manner. Using optogenetics to drive VTA GABA/glutamate co-release in downstream structures that regulate mood and motivation, I will apply gene-editing tools (CRISPR/Cas9) to test the selective contribution of GABA vs. glutamate release in behavioral reinforcement (Aim 1). I will then apply chemogenetic approaches and chronic behavioral manipulations that alter postsynaptic activity to test the net in vivo effect of optogenetically driving VTA GABA/glutamate co-release using in vivo calcium imaging (Aim 2). These experiments will reveal basic mechanisms of neurotransmitter co-release and uncover their role within mesolimbic circuitry in balancing motivation and preventing prolonged excitation/inhibition of efferent structures associated with extreme motivational states. The capability of GABA/glutamate co-release to normalize activity can provide a novel target for treating disorders of imbalanced motivation such as bipolar disorder or depression. A strong interdisciplinary team of faculty mentors and experts will provide the scientific training required for these proposed experiments (gene-editing and fiber photometry) as well as professional development training to facilitate a successful transition to the R00 phase of this proposal. During the R00 phase, I will unify my prior expertise with newly acquired skills to determine the physiological and behavioral role of a newly-described VTA GABA/glutamate projection to amygdala. Using in vivo calcium imaging, I will first monitor activity of VTA GABA/glutamate terminals in amygdala during an effort-based instrumental sucrose task, and will then identify the net effect of optogenetically stimulating VTA GABA/glutamate terminals on cell-defined amygdala populations (Aim 3). These results will significantly expand our understanding of the role of VTA co-release in complex motivated behavior relevant to models of bipolar disorder and depression, and will crucially pave the way for more targeted approaches that form the basis my independent research program.