CNS Pathways Regulating Ghrelin Effects on Body Weight

描述(申请人提供)：下丘脑弓状核中两种不同的肽能神经元(POMC和NPY/AgRP)对瘦素等代谢信号做出反应。另一种关键的代谢激素，Ghrelin，已经被发现可以调节食物摄入量和体重。有证据表明，中枢神经系统神经元群是Ghrelin的靶点。这包括弓状核中的NPY/AgRP神经元。这个项目将使用最先进的功能神经解剖学技术，包括轨迹追踪，使用原位杂交组织化学技术诱导Ghrelin诱导的基因表达，以及(单独和联合)神经元表型的化学鉴定，以确定Ghrelin反应神经元的解剖投射。我们将确定在表达NPY/AGRP和POMC/CART的弓状和交叉后神经元中，Ghrelin反应神经元群体投射到脊髓、迷走神经背侧运动核、下丘脑外侧区和室旁核等部位的程度，这些部位可能在激活Ghrelin激活的传出通路中发挥不同的作用。我们将直接验证这一假设，即仅在弓状核、下丘脑腹内侧核和迷走神经背侧复合体的神经元中表达的Ghrelin足以介导Ghrelin增加食物摄入量和减少能量消耗的作用。为了实现这一点，我们将使用一种新的小鼠模型，该模型对Ghrelin受体的表达为空。小鼠是这样制作的，即Crerecombinase的作用将重新激活ghrelin受体的表达。我们将把我们的小鼠交叉到AgRP-Cre和SF-1-Cre小鼠，这将导致Ghrelin受体只在弓状核和腹内侧核表达。我们还将向背侧迷走神经复合体注射腺相关病毒载体，以将Cre重组酶输送到背侧迷走神经复合体。在所有小鼠中，我们将评估野生型、空白型和复活型小鼠对急性Ghrelin注射的反应和对饮食诱导肥胖的敏感性。这些研究将极大地扩展我们对Ghrelin参与的神经回路的了解。

DESCRIPTION (provided by applicant): Two distinct populations of peptidergic (POMC and NPY/AgRP) neurons in the arcuate nucleus of the hypothalamus respond to metabolic cues such as leptin. Another critical metabolic hormone, ghrelin, has been identified to regulate food intake and body weight. Evidence suggests that CNS neuronal groups are targets of ghrelin. This includes NPY/AgRP neurons in the arcuate nucleus. This project will employ state of the art functional neuroanatomical techniques including tract tracing, ghrelin induced gene expression using in situ hybridization histochemistry, and chemical identification of neuronal phenotypes (alone and in combination) to identify the anatomical projections of ghrelin-responsive neurons. We will determine to what degree populations of ghrelin responsive neurons in the arcuate and retrochiasmatic neurons expressing NPY/AGRP and POMC/CART project to sites including spinal cord, dorsal motor nucleus of the vagus, the lateral hypothalamic area and the paraventricular nucleus, which are likely to play a distinct role in activating the efferent pathways activated by ghrelin. We will directly test the hypothesis that ghrelin receptor expression only in neurons in the arcuate nucleus, ventromedial hypothalamic nucleus, and the dorsal vagal complex is sufficient to mediate the effects of ghrelin to increase food intake and decrease energy expenditure. To accomplish this we will use a novel mouse model that is null for ghrelin receptor expression. The mouse is made such that the action of Crerecombinase will reactivate ghrelin receptor expression. We will cross our mice to AgRP-Cre and SF-1-Cre mice, which will result in mice with ghrelin receptor expression only in the arcuate and ventromedial nuclei. We will also inject the dorsal vagal complex with adeno-associated viral vectors to deliver Cre-recombinase to the dorsal vagal complex. In all mice, we will assess the responses to acute ghrelin administration and sensitivity to diet induced obesity in wild type, null, and reactivated mice. These studies will substantially expand our knowledge of the neural circuits engaged by ghrelin.