5-HT NEURONS AND MEAL REGULATION

项目总结 尽管肥胖率快速增长，减肥研究也付出了巨大努力，但 安全有效的治疗方法已取得显著进展，但仍然有限，这主要是由于不足。 了解大脑如何管理体重和进食。5-羟色胺受体--氯酪蛋白 激动剂，显示出有效减肥的巨大希望，但由于癌症风险增加而被停用 发展。5-羟色胺仍然是抗肥胖治疗的一个极好的潜在靶点，但还需要更多的工作来 以确定靶向5-羟色胺的最有效方法。以前在这方面的工作已经表明 GABA和多巴胺对5-羟色胺神经元的抑制是调节小鼠摄食的关键。事实上，我的初选 研究表明，2(GABA受体亚单位)在TPH2(5-羟色胺合成限速酶)中缺失 与野生型小鼠相比，神经元导致进食次数减少和进食间隔延长，这表明 进餐开始时潜在的功能障碍。此外，DRD2(一种多巴胺受体)的缺失减少了微型 TPH2神经元的抑制性突触后电流(MIPSC)，表明DRD2在 介导5-羟色胺神经元对GABA抑制输入的反应。最后，我发现在饥饿的小鼠身上，选择性的 大鼠中缝背核向弓状核投射的5-羟色胺能神经元的激活 与对照组相比，进食过程中的下丘脑显著减少了食物的摄入量。已被占用 综上所述，这些初步数据让我得出这样的假设，即5-HTDRN神经元的GABA输入受到调控，在 部分，通过DRD2，并可能有助于调节进食开始。这项建议的重点是1)确定 5-HTDRNGABA-ARH回路是否调节进食起始和2)确定DA是否影响→ 向ARH投射的5-HTDRN神经元发出信号以启动进食。为了实现这些目标，我将研究(1) 进食过程中5-HTDRNARH环路的光刺激或光抑制是否会改变膳食 (2)ARH投射的5-HTDRN神经元在进食前或进食过程中的动态活动 在进餐开始、进食和结束进餐时，使用纤维光度法。更进一步，我将产生老鼠 选择性缺失ARH投射的5-γ神经元中的GABAA DRD2亚单位或DA受体DRD2 并进行代谢和膳食模式研究，以及(2)检查电生理特性(mIPSC， 静息膜电位、动作电位放电及其对GABA或DRD2激动剂的反应 投射5-羟色胺能神经元，其中的GABAA DRD2亚单位或DA受体γ2缺失。有了支持 从这笔奖学金中，我将利用贝勒医学院的广泛资源来扩大我的专业知识 这样我就可以在我的事业上有所进步，并学习更新颖和更全面的方法来研究 启动进餐的机制。这个机会将为我提供必要的工具，以提高我的 培训并朝着成为一名学术机构的独立研究科学家的职业目标迈进 机构。

PROJECT SUMMARY Despite the rapidly growing rate in obesity and tremendous efforts in weight loss research, the development of safe and effective therapeutics has progressed significantly, yet is still limited, largely due to insufficient understanding of how the brain manages body weight and feeding. Lorcaserin, a 5-HT (serotonin) receptor agonist, showed great promise for effectively reducing weight, but was withdrawn due to increased risk for cancer development. 5-HT remains an excellent potential target for an anti-obesity therapeutic, but more work needs to be completed to determine the most effective way for targeting 5-HT. Previous work in this area has shown that GABA and dopamine inhibition of 5-HT neurons is critical for mediating food intake in mice. In fact, my preliminary work has revealed that 2 (GABA receptor subunit) deletion in TPH2 (rate limiting enzyme for 5-HT synthesis) neurons causes a decreased meal number and increased meal interval compared to wild-type mice, indicating a potential dysfunction in meal initiation. Furthermore, DRD2 (a dopamine receptor) deletion reduced miniature inhibitory post synaptic current (mIPSC) in TPH2 neurons, indicating that DRD2 plays an essential role in mediating 5-HT neuronal response to GABA inhibitory input. Finally, I found that in hungry mice, the selective activation of 5-HT neurons in the Dorsal Raphe Nucleus (DRN) which project to the Arcuate Nucleus (ARH) in the Hypothalamus during food approach significantly reduces food intake compared to control mice. Taken together, these preliminary data led me to the hypothesis that GABA inputs to 5-HTDRN neurons are regulated, in part, by DRD2 and may contribute to the regulation of meal initiation. The focus of this proposal is to 1) determine whether the 5-HTDRN→ARH circuit regulates meal initiation and 2) to determine whether DA influences GABA signaling to ARH-projecting 5-HTDRN neurons for meal initiation. To achieve these goals, I will examine (1) whether photostimulation or photoinhibition of the 5-HTDRN→ARH circuit during food approach alters meal initiation and food intake, and (2) the dynamic activity of ARH-projecting 5-HTDRN neurons before or during food approach, at meal initiation, eating and meal termination using fiber photometry. Further, I will generate mice with a selective deletion of either the GABAA γ2 subunit or DA receptor DRD2 in ARH-projecting 5-HTDRN neurons and perform metabolic and meal pattern studies, and (2) examine the electrophysiological properties (mIPSC, resting membrane potential, action potential firing, and their responses to GABA or DRD2 agonists) of ARH- projecting 5-HTDRN neurons in which either the GABAA γ2 subunit or DA receptor DRD2 is deleted. With support from this fellowship, I will utilize the extensive resources at Baylor College of Medicine to expand my expertise so that I can advance in my career and learn more novel and comprehensive approaches to studying the mechanisms underlying meal initiation. This opportunity will provide me with the necessary tools to enhance my training and move toward my career goal of becoming an independent research scientist at an academic institution.