Effect of killing or removing GABA from NPY/AgRP neurons

描述(申请人提供)：我们正在进行引人注目的观察，即消融成年小鼠下丘脑AgRP神经元，而不是新生小鼠，会导致严重的厌食症。我们发现，这种厌食症是由于臂旁核(PBN)的AgRP神经元突然失去GABA信号所致，这表明向臂旁核(PBN)慢性注入苯二氮卓类GABAA受体激动剂可以预防致死性厌食，但其他核团无法预防这种致命性厌食。我们假设，PBN的平衡输入维持正常的进食，PBN的过度活动(例如，由于GABA的丧失)会导致厌食症。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(S)和受体(S)。我们还建议发现在关键的PBN神经元中特异表达的介导厌食症的基因，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、跟踪和电生理研究。我们的实验表明，当GABAA激动剂(Bretazenil)、5HT3拮抗剂(恩丹西酮)、LiCl或暴露在高脂饮食中时，小鼠可以适应AgRP神经元的丧失并恢复正常进食。我们将探索这样的假设，即这些治疗导致PBN的神经元输入或输出的适应，或相关PBN神经元本身的可塑性。我们预计，这些实验将描绘出对维持正常摄食行为非常重要的神经回路。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该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一电路如何适应不断变化的环境条件，并确定涉及的分子和细胞变化。这项研究对于更好地理解正常和成瘾的摄食行为、神经元的可塑性以及神经性厌食症等疾病是相关的。

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.