CNS Pathways Regulating Ghrelin Effects on Body Weight

描述（由申请人提供）：下丘脑弓状核中的两种不同的肽能神经元（POMC和NPY/AgRP）对瘦素等代谢线索作出反应。另一种关键的代谢激素，胃饥饿素，已被确定调节食物摄入和体重。有证据表明中枢神经系统神经元群是胃饥饿素的目标。这包括弓形核中的NPY/AgRP神经元。该项目将采用最先进的功能神经解剖学技术，包括束示踪，利用原位杂交组织化学技术诱导ghrelin基因表达，以及神经元表型的化学鉴定（单独或联合），以确定ghrelin反应神经元的解剖投影。我们将确定表达NPY/AGRP和POMC/CART的弓形和后交叉神经元中胃饥饿素反应神经元的群体在多大程度上投射到脊髓、迷走神经背运动核、下丘脑外侧区和室旁核等部位，这些部位可能在激活胃饥饿素激活的输出通路中发挥独特的作用。我们将直接验证胃饥饿素受体仅在弓状核、下丘脑腹内侧核和迷走神经背侧复合体神经元中的表达足以介导胃饥饿素增加食物摄入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，它是饥饿素受体表达的零。小鼠是这样制造的，creerecombinase的作用将重新激活胃饥饿素受体的表达。我们将小鼠与AgRP-Cre和SF-1-Cre小鼠杂交，这将导致仅在弓形核和腹内侧核中表达胃饥饿素受体的小鼠。我们还将向迷走背复合体注射腺相关病毒载体，以将cree -重组酶传递到迷走背复合体。在所有小鼠中，我们将评估野生型、无效型和再激活型小鼠对急性胃饥饿素的反应和对饮食诱导肥胖的敏感性。这些研究将大大扩展我们对胃饥饿素所参与的神经回路的认识。

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.