Effect of killing or removing GABA from NPY/AgRP neurons

描述（由申请人提供）：我们正在进行一项惊人的观察，即在成年小鼠（而不是新生小鼠）中，下丘脑AgRP神经元的消融会导致严重的厌食症。我们发现厌食症是由于AgRP神经元向臂旁核（PBN）的GABA信号的突然丢失，表明慢性输注苯二氮卓类GABAA受体激动剂可以预防致死的厌食症，而不是其他核。我们假设PBN的平衡输入维持了正常的摄食，而PBN的过度活动（例如由于GABA的损失）导致厌食症。我们建议使用药理学和遗传学工具来确定PBN的兴奋来源，以及涉及的神经递质和受体。我们还建议发现一个在介导厌食症的关键PBN神经元中特异性表达的基因，然后将Cre重组酶靶向该基因，这将极大地促进进一步的遗传、追踪和电生理研究。我们的实验表明，当长期使用GABAA激动剂（bretazenil）、5HT3拮抗剂（ondansetron）、LiCl或暴露于高脂肪饮食时，小鼠可以适应AgRP神经元的丧失并恢复正常饮食。我们将探讨这些治疗导致PBN神经元输入或输出的适应性，或相关PBN神经元本身的可塑性的假设。我们预计，这些实验将描绘一个神经回路，是重要的维持正常的摄食行为。我们已经建立了强大的药理学和遗传学技术，这将使我们能够识别神经回路中神经元使用的关键神经递质和受体。我们的最终目标是了解这个回路如何适应不断变化的环境条件，并确定所涉及的分子和细胞变化。这项研究有助于更好地理解正常和成瘾的进食行为、神经元可塑性以及神经性厌食症等疾病。

DESCRIPTION (provided by applicant): We are pursuing the striking observation that ablation of hypothalamic AgRP neurons in adult, but not neonatal, mice results in severe anorexia. We discovered that the anorexia is due to sudden loss of GABA signaling by AgRP neurons to the parabrachial nucleus (PBN) by showing that the lethal anorexia can be prevented by chronic infusion of a benzodiazepine GABAA receptor agonist into the PBN, but not other nuclei. We hypothesize that balanced input to the PBN maintains normal feeding and that excessive activity of the PBN (e.g. due to loss of GABA) results in anorexia. We propose to identify the source of the excitation to the PBN, as well as the neurotransmitter(s) and receptor(s) involved using pharmacological and genetic tools. We also propose to discover a gene that is specifically expressed in the critical PBN neurons that mediate anorexia, and then target Cre recombinase to that gene, which would greatly facilitate further genetic, tracing and electrophysiological studies. Our experiments indicate that mice can adapt to loss of AgRP neurons and resume normal eating, when chronically treated with a GABAA agonist (bretazenil) a 5HT3 antagonist (ondansetron), LiCl or exposed to a high-fat diet. We will explore the hypothesis that these treatments lead to adaptations in neuronal inputs or outputs of the PBN, or plasticity within the relevant PBN neurons themselves. We anticipate that these experiments will delineate a neural circuit that is important for maintenance of normal feeding behavior. We have established powerful pharmacological and genetic techniques that will allow us to identify the critical neurotransmitters and receptors that are used by neurons within that circuit. Our ultimate goals are to understand how this circuit adapts to changing environmental conditions and identify the molecular and cellular changes involved. This research is relevant to a better understanding normal and addictive feeding behavior, neuronal plasticity, and diseases such as anorexia nervosa.