Appetite: Serotonin and corticotropin releasing factor

描述(申请人提供)：本研究旨在研究下丘脑室旁核(PVN)内5-羟色胺(5-HT)及其相关神经元对大鼠神经元促肾上腺皮质激素释放因子(CRF)基因表达和摄食行为的影响。下丘脑室旁核CRF神经元是控制摄食行为的重要中介，如外源性应用CRF或刺激CRF神经元导致摄食抑制。同样，刺激大脑中突触5-羟色胺传递的药物也众所周知会抑制食物的摄入。在解剖学上，也已知在PVN CRF神经元上存在5-羟色胺终末投射，这表明5-羟色胺可能通过对PVN CRF神经元发挥迄今尚未明确的作用而抑制食欲。在PVN CRF细胞体中存在与食欲调节相关的5-羟色胺受体亚型的mRNAs的数据进一步支持了5-羟色胺之间潜在的功能联系。值得注意的是，尽管有一些研究提出了建议，但到目前为止还没有明确的研究表明，5-羟色胺相关药物确实可能通过刺激CRF mRNA的产生和CRF蛋白的表达来抑制摄食。在这一设想中，我们假设5-羟色胺(5-HT)与神经肽(如CRF和黑素细胞刺激素(αMSH))之间存在功能联系，它们分别位于下丘脑室旁核(5-HT，CRF)和弓状核(ARC)(αMSH)。我们的具体目标是：(1)确定5-羟色胺的释放是否调节下丘脑室旁核的CRF或α-MSH神经元以抑制摄食；(2)确定5-羟色胺的释放是否通过驻留在弓状核的1-MSH神经元及其相关神经元间接调节下丘脑的CRF神经元；以及(3)确定下丘脑CRF及其相关神经元的下游靶点。在我们的实验设计中，我们将使用芬氟拉明(Fen)，这是一种强烈促进5HT突触传递的药物。中枢性和全身性FEN给药将被用来评估用5-羟色胺受体拮抗剂预先处理的大鼠的PVN CRF mRNA的表达，这些受体拮抗剂是与食欲相关的PVN CRF神经元(5HT-1B、2A和2C亚型)。5-羟色胺是否间接影响下丘脑室旁核CRF基因的表达；1-MSH释放到CRF神经元上具有刺激性；因此，FEN可能通过增加1-MSH信号来刺激CRF神经元。RNA干扰将被用来消除CRF mRNA，以确定Fen启动的5-HT是否通过额外的下游机制影响食欲抑制。这些研究应该提供新的洞察特征的5HT-CRF突触连接在控制食物摄入中的作用，并最终有助于理解这种连接是否以及如何对整体能量平衡的调节以及肥胖症、厌食症和其他与食欲相关的健康问题的病因。本研究旨在探讨下丘脑室旁核(PVN)内5-羟色胺(5-HT)及其相关神经元对大鼠神经促肾上腺皮质激素释放因子(CRF)基因表达及摄食行为的影响。这些研究应该提供新的洞察特征的5HT-CRF突触连接在控制食物摄入中的作用，并最终有助于理解这种连接是否以及如何对整体能量平衡的调节以及肥胖症、厌食症和其他与食欲相关的健康问题的病因。

DESCRIPTION (provided by applicant): This proposal investigates the influence of serotonin (5-HT) and its associated neurons in the hypothalamic paraventricular nuclei (PVN) on neuronal corticotropin releasing factor (CRF) mRNA expression and feeding behavior in rats. PVN CRF neurons are important mediators in the control of feeding behavior; e.g. exogenous application of CRF or stimulation of CRF neurons result in the inhibition of food intake. Similarly, drugs that stimulate synaptic 5-HT transmission in the brain are also well known to inhibit food intake. Anatomically, it is also known that 5-HT terminal projections are found on PVN CRF neurons; this suggests that 5HT agents may suppress appetite through heretofore uncharacterized actions on PVN CRF neurons. A potential functional link between 5-HT is further supported by data demonstrating the presence of mRNAs for 5-HT receptor subtypes linked to appetite regulation in PVN CRF cell bodies. Remarkably, despite the suggestion of a number of studies, there have been no definitive studies to date demonstrating that 5-HT-associated drugs may indeed suppress feeding by stimulating CRF mRNA production and CRF protein expression. In this proposal, we hypothesize that there exists a functional link between serotonin (5-HT) and neuropeptides, such as CRF and melanocyte stimulating hormone (alpha MSH) and their respective neurons residing within the PVN (5-HT, CRF) and the arcuate (ARC) hypothalamic nuclei (alpha MSH), respectfully. Our Specific Aims are to (1) determine if 5-HT release regulates CRF or alpha MSH neurons in the PVN to suppress food intake; (2) Determine if 5-HT release indirectly regulates CRF neurons in the PVN via 1-MSH neurons residing in the arcuate and its associated neurons; and (3) determine downstream targets of hypothalamic CRF and its associated neurons. In our experimental design, we will utilize fenfluramine (FEN), a drug that strongly promotes 5HT synaptic transmission. Central and systemic FEN administration will be used to assess PVN CRF mRNA expression in rats pre-treated with 5-HT receptor antagonists specific to PVN CRF neurons that are appetite-linked (the 5HT-1B, 2A, & 2C subtypes). FEN will also be used to test whether 5-HT affects PVN CRF mRNA expression indirectly; 1-MSH release onto CRF neurons is stimulatory; hence, FEN could stimulate CRF neurons by increasing 1-MSH signaling. RNA interference will be used to eliminate CRF mRNA, to determine if FEN-initiated 5-HT influences appetite suppression by additional downstream mechanisms. These studies should provide new insight into the role of a poorly characterized 5HT-CRF synaptic connection in the control of food intake, and ultimately contribute to understanding if and how this connectivity is important to the regulation of overall energy balance, and the etiology of obesity, anorexia, and other appetite-related health problems. This proposal investigates the influence of serotonin (5-HT) and its associated neurons in the hypothalamic paraventricular nuclei (PVN) on neuronal corticotropin releasing factor (CRF) mRNA expression and feeding behavior in rats. These studies should provide new insight into the role of a poorly characterized 5HT-CRF synaptic connection in the control of food intake, and ultimately contribute to understanding if and how this connectivity is important to the regulation of overall energy balance, and the etiology of obesity, anorexia, and other appetite-related health problems.