AGRP NEURONS. NMDARs, Spines, Source of Excitatory Input and Downstream Effectors

AGRP 神经元。

• 批准号: 8479355
• 负责人: BRADFORD B LOWELL
• 金额: $ 51.94万
• 依托单位: BETH ISRAEL DEACONESS MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8479355
• 关键词: Afferent Neurons; Anatomy; Animals; Anorexia; Area; Attention; Automobile Driving; Behavior; Body fat; Brain; Collaborations; Complex; Dendritic Spines; Eating; Eating Disorders; Excitatory Synapse; FOS gene; Fasting; Feeding behaviors; Food; Genes; Glutamates; Growth; Hormones; Laser Scanning Microscopy; Lateral; Leptin; Light; Maps; Mediating; Metabolism; Microscopy; Mind; Mus; N-Methyl-D-Aspartate Receptors; Nerve; Neurobiology; Neurons; Obesity; Pharmacogenetics; Photons; Play; Potassium Channel; Rabies; Regulation; Relative (related person); Role; Signal Transduction; Source; Synapses; Synaptic Transmission; Synaptic plasticity; Technology; Vertebral column; Weight; Work; awake; base; feeding; gamma-Aminobutyric Acid; ghrelin; hormone regulation; in vivo; innovation; mRNA Expression; neural circuit; neuroregulation; optogenetics; parabrachial nucleus; postsynaptic; prevent; relating to nervous system; synaptogenesis; tomography; transmission process

DESCRIPTION (provided by applicant): The brain regulates feeding behavior and metabolism however the neurocircuitry responsible for this is largely unknown. The complexity of the brain and the need to manipulate it in awake, behaving animals, represent significant technical challenges. The application of new, innovative approaches is likely to greatly accelerate progress. Recently, we and others, using pharmacogenetic and optogenetic technology, have discovered that AgRP neurons drive intense feeding behavior. With this in mind, it is now critical to determine the afferent signals (hormones and neural inputs) controlling AgRP neuron activity as well as the effectors (GABA, NPY, AgRP, and downstream neural circuits) that bring about AgRP neuron-driven feeding. Remarkably, little attention has been paid to afferent (upstream) neural inputs regulating AgRP neurons. This is unfortunate because a) defective neural control of AgRP neurons could contribute importantly to complex eating disorders (ranging from anorexia to obesity), and b) the hormonal regulation of AgRP neurons, one example being ghrelin, likely works by modulating these inputs. Recently, in Preliminary Studies, we discovered that NMDA receptors (NMDARs), key regulators of excitatory synaptic plasticity, play a critical role in regulating AgRP neuron activity and feeding; NMDARs on POMC neurons, on the other hand, play little or no role. Consistent with this, AgRP neurons have abundant dendritic spines (postsynaptic specializations where most excitatory synapses reside and within which NMDARs operate to control plasticity); POMC neurons, in contrast, lack spines. Finally, we have found that fasting-activation of AgRP neurons require NMDARs and involves dendritic spinogenesis, and very likely increased excitatory synaptogenesis. Thus, NMDAR-mediated plasticity of excitatory input to AgRP neurons plays a key, previously unknown role in regulating AgRP neuron activity and consequently feeding behavior. The present application will pursue key implications of the above-mentioned findings. In Aim 1, using advanced 2-photon microscopy, we will mechanistically investigate "regulatory" plasticity of excitatory inputs, via NMDARs/spines, to AgRP neurons. In Aim 2, using Cre-dependent, Monosynaptic Rabies Mapping and also Channelrhodopsin-Assisted Circuit Mapping, we will identify and assess function of afferent neurons sending glutamatergic input to AgRP neurons. In Aim 3, using pharmacogenetic activation of AgRP neurons unable to signal via GABA, NPY and/or AgRP and also anatomic-selective, optogenetic activation of AgRP nerve terminals, we will identify the downstream effectors (transmitters and circuits) of AgRP neurons.

描述（由申请人提供）：大脑调节进食行为和新陈代谢，但负责此的神经回路在很大程度上是未知的。大脑的复杂性以及在清醒、有行为能力的动物中操纵大脑的需要是重大的技术挑战。新的创新方法的应用可能会大大加速进展。最近，我们和其他人利用药物遗传学和光遗传学技术，发现 AgRP 神经元驱动强烈的摄食行为。考虑到这一点，现在至关重要的是确定控制 AgRP 神经元活动的传入信号（激素和神经输入）以及带来 AgRP 神经元驱动喂养的效应器（GABA、NPY、AgRP 和下游神经回路）。值得注意的是，很少有人关注调节 AgRP 神经元的传入（上游）神经输入。这是不幸的，因为 a) AgRP 神经元的神经控制缺陷可能会导致复杂的饮食失调（从厌食症到肥胖），b) AgRP 神经元的激素调节（一个例子是生长素释放肽）可能通过调节这些输入来发挥作用。最近，在初步研究中，我们发现NMDA受体（NMDAR）是兴奋性突触可塑性的关键调节因子，在调节AgRP神经元活动和摄食方面发挥着关键作用；另一方面，POMC 神经元上的 NMDAR 几乎没有发挥作用。与此一致的是，AgRP 神经元具有丰富的树突棘（突触后特化，其中大多数兴奋性突触驻留，并且 NMDAR 在其中控制可塑性）；相比之下，POMC 神经元缺乏刺。最后，我们发现 AgRP 神经元的禁食激活需要 NMDAR，并涉及树突棘发生，并且很可能增加兴奋性突触发生。因此，NMDAR 介导的 AgRP 神经元兴奋性输入的可塑性在调节 AgRP 神经元活动以及随后的摄食行为中发挥着之前未知的关键作用。本申请将探究上述发现的关键含义。在目标 1 中，我们将使用先进的 2 光子显微镜，从机制上研究通过 NMDAR/刺向 AgRP 神经元的兴奋性输入的“调节”可塑性。在目标 2 中，我们将使用 Cre 依赖性单突触狂犬病图谱以及视紫红质通道辅助电路图谱来识别和评估传入神经元向 AgRP 神经元发送谷氨酸能输入的功能。在目标 3 中，利用无法通过 GABA、NPY 和/或 AgRP 发出信号的 AgRP 神经元的药物遗传学激活以及 AgRP 神经末梢的解剖选择性、光遗传学激活，我们将识别 AgRP 神经元的下游效应器（递质和电路）。