A direct LH to PVH projection for antagonistic regulation of feeding

项目摘要 治疗肥胖症的治疗药物的开发一直没有成功，原因是副作用和 疗效有限。我的长期研究目标是描绘出影响体重的神经通路 动态平衡，并为有效和特定的治疗肥胖症提供了框架。尽管令人兴奋 在理解由刺鼠相关蛋白(AgRP)神经元调节的摄食行为方面取得了进展， 这些神经元只代表了Arc GABA能神经元的一小部分，而大多数其他神经元的作用 下丘脑神经元对摄食的调节尚不清楚。 最近的研究表明，激活外侧下丘脑(LH)谷氨酸能神经元会抑制摄食， 这与黄体生成素损毁所致的吞噬功能低下的表型形成鲜明对比，提示其他 黄体生成素能神经元，包括GABA能神经元，参与摄食调节。我们之前曾演示过，当 通道视紫红质2(ChR2)在LHPdx1-Cre神经元中表达，光刺激表达ChR2的纤维 位于PVH诱导的贪婪摄食，依赖于GABA的释放。此外，GABA的干扰 促黄体生成素神经元释放减少摄食和体重，提示与促黄体生成素GABA能有生理联系 神经元对摄食的调节。我们的初步数据显示，LHPdx1-Cre神经元发出单突触 下丘脑室旁核神经元兴奋性和抑制性传入及缺乏→释放的LHGABA-Pdx1-Cre纤维的激活 在PVH中抑制快速复食。这些结果，结合之前的结果，PVH神经元 活动水平决定了促进摄食与抑制摄食，促使我们假设竞争抑制和 兴奋性单突触的LH、→、PVH投射通过控制PVHMC4R神经元的活动来调节摄食。 目的1)选择性激活抑制性黄体生成素-→-PVH投射在促进摄食中的作用 由PVH介导；2)抑制LH、→、PVH、GABA能纤维是否足以减少摄食 行为。目的2测试1)选择性激活兴奋性Lh、→、PVH投射是否抑制快速再摄食； 2)LHPdx1-Cre神经元是否需要释放谷氨酸来抑制摄食；3)是否需要摄食 Lh、→、PVH、谷氨酸能投射引起的抑制作用是由PVH介导的。目标3将决定是否 Lh、→、PVH、GABA能和谷氨酸能单突触投射靶向和调节PVHMC4R活性 神经元分别对摄食起促进或抑制作用。 结果将首次建立竞争和平行的谷氨酸能和GABA能的LHPVH→ 通过控制PVH MC4R神经元活动而在摄食中扮演相反角色的投射，将代表 在理解喂养调节的神经基础方面迈出了重要的一步。

Project Summary The development of therapeutic drugs to cure obesity has not been successful due to unwanted side effects and limited efficacy. My long term research goal is to delineate neural pathways responsible for body weight homeostasis, and provide a framework for effective and specific therapeutics against obesity. Despite exciting progress has been made in understanding feeding behavior regulated by agouti-related protein (AgRP) neurons, these neurons only represent a small percent of Arc GABAergic neurons and the role of the majority of other hypothalamic neurons in feeding regulation is unknown. Recent studies suggest that activation of the lateral hypothalamus (LH) glutamatergic neurons inhibit feeding, which is in stark contrast to the hypophagia phenotype induced by LH lesion, suggesting a potential role of other LH neurons, including GABAergic neurons in feeding regulation. We previously demonstrated that, when channelrhodopsin2 (ChR2) is expressed in LH Pdx1-Cre neurons, photo-stimulation of ChR2-expressing fibers located in the PVH induced voracious feeding, which depends on GABA release. In addition, disruption of GABA release from LH neurons reduces feeding and body weight, suggesting physiological relevance for LH GABAergic neurons in feeding regulation. Our preliminary data showed that LH Pdx1-Cre neurons send monosynaptic excitatory and inhibitory inputs to PVH neurons and that activation of LH→Pdx1-Cre fibers lacking GABA release in the PVH inhibited fast-refeeding. These results, in combination with the previous results that PVH neuron activity levels dictate feeding promotion versus inhibition, prompt us to hypothesize that competing inhibitory and excitatory monosynaptic LH→PVH projections regulate feeding through controlling PVH MC4R neuron activity. Aim 1 will determine whether 1) selective activation of inhibitory LH→PVH projections in feeding promotion is mediated by PVH; and 2) whether inhibition of LH→PVH GABAergic fibers is sufficient to reduce feeding behavior. Aim 2 will test 1) whether selective activation of excitatory LH→PVH projections inhibits fast-refeeding; 2) whether glutamate release from LH Pdx1-Cre neurons is required for feeding inhibition; 3) whether feeding inhibition elicited by LH→PVH glutamatergic projections is mediated by PVH. Aim 3 will determine whether LH→PVH GABAergic and glutamatergic monosynaptic projections target and modulate the activity of PVH MC4R neurons to exert effects on feeding promotion or inhibition, respectively. The results will establish, for first time, competing and parallel glutamatergic and GABAergic LH→PVH projections that play opposite roles in feeding by controlling PVH MC4R neuron activity and will represent a significant step in understanding the neural basis for feeding regulation.