5-HT NEURONS AND MEAL REGULATION

项目摘要 尽管肥胖率迅速增长，减肥研究也付出了巨大努力， 安全和有效的治疗方法已经取得了显着进展，但仍然有限，主要是由于不足， 了解大脑如何管理体重和进食。氯卡色林，一种5-HT（血清素）受体 激动剂，显示出有效减轻体重的巨大希望，但由于癌症风险增加而被撤回 发展5-HT仍然是抗肥胖治疗的一个很好的潜在靶点，但还需要更多的工作， 以确定针对5-HT的最有效方法。这一领域以往的工作表明， GABA和多巴胺对5-HT神经元的抑制对于介导小鼠的食物摄入至关重要。事实上，我的初步调查 研究表明，TPH 2（5-HT合成限速酶）中的GABA受体亚基（GABA 2）缺失 与野生型小鼠相比，神经元引起进餐次数减少和进餐间隔增加，表明 进食启动的潜在功能障碍。此外，DRD 2（多巴胺受体）缺失减少了微 抑制性突触后电流（mIPSC）在TPH 2神经元，表明DRD 2起着重要作用， 介导5-HT神经元对GABA抑制性输入的反应。最后，我发现在饥饿的老鼠中， 中缝背核（DRN）中投射到弓状核（ARH）的5-HT神经元激活， 与对照小鼠相比，在食物接近期间下丘脑显著减少食物摄入。采取 总之，这些初步的数据使我假设GABA输入到5-HTDRN神经元是受调节的， 部分，通过DRD 2，并可能有助于调节进餐开始。本提案的重点是：（1）确定 5-HTDRN→ARH回路是否调节进餐开始和2）确定DA是否影响GABA 向投射ARH的5-HTDRN神经元发出进食起始的信号。为了实现这些目标，我将研究（1） 食物接近过程中5-HTDRN→ARH回路的光刺激或光抑制是否会改变膳食 启动和食物摄入，以及（2）在食物之前或期间ARH投射5-HTDRN神经元的动态活动 方法，在进餐开始，进食和进餐结束时使用纤维光度法。此外，我将生成小鼠 在ARH投射的5-HTDRN神经元中选择性缺失GABAA γ2亚基或DA受体DRD 2， 并进行代谢和膳食模式研究，以及（2）检查电生理学特性（mIPSC， 静息膜电位、动作电位放电及其对GABA或DRD 2激动剂的反应）。 投射5-HTDRN神经元，其中GABAA γ2亚基或DA受体DRD 2缺失。支持下 通过这次奖学金，我将利用贝勒医学院的广泛资源来扩展我的专业知识 这样我就可以在我的职业生涯中前进，学习更多新颖和全面的方法来研究 膳食启动的潜在机制。这个机会将为我提供必要的工具，以提高我的 培训和走向我的职业目标，成为一个独立的研究科学家在学术 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 Lorcaserin, a 5-HT (serotonin) receptor agonist, showed great promise for effectively reducing weight, but was withdrawn due to increased risk for cancer development. 5-HT remains an excellent potential target for an anti-obesity therapeutic, but more work needs to be completed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.